| **Derivative Financial Instruments and Risk Management (Tables)**                                                       | 9 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
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| **Derivative Instruments and Hedging Activities Disclosure [Abstract]**                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
| Location and fair value of derivative instruments reported in the Consolidated Statements of Financial Position         | The location and fair value of derivative instruments reported in the Consolidated Statements of Financial Position were as follows:(Millions of dollars)        Asset (Liability) Fair Value Consolidated Statements ofFinancial Position Location September 30, 2015 December 31, 2014Designated derivatives     Interest rate contractsOther assets $66 $79Interest rate contractsAccrued expenses (4) (8)   $62 $71Undesignated derivatives     Foreign exchange contractsOther assets $3 $5Foreign exchange contractsAccrued expenses (5) (15)Cross currency contractsOther assets 35 17   $33 $7                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
| Deferred gains (losses) recorded in AOCI on the Consolidated Statements of Changes in Stockholder's Equity              | For the nine months ended September 30, 2015 and 2014, the deferred gains (losses) recorded in AOCI on the Consolidated Statements of Changes in Stockholder’s Equity associated with our cash flow interest rate contract hedges were as follows:(Millions of dollars) Balance as of December 31, 2014, net of tax (expense)/benefit of $3$(5)Gains (losses) deferred during the period, net of tax (expense)/benefit of $(1)—(Gains) losses reclassified to earnings, net of tax expense/(benefit) of $(1)3Balance as of September 30, 2015, net of tax (expense)/benefit of $1$(2)  (Millions of dollars) Balance as of December 31, 2013, net of tax (expense)/benefit of $3$(5)Gains (losses) deferred during the period, net of tax (expense)/benefit of $2(5)(Gains) losses reclassified to earnings, net of tax expense/(benefit) of $(1)3Balance as of September 30, 2014, net of tax (expense)/benefit of $4$(7)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| Schedule of effect of derivatives designated as fair value hedging instruments in the Consolidated Statements of Profit | The effect of derivatives designated as hedging instruments on the Consolidated Statements of Profit was as follows:Fair Value Hedges(Millions of dollars)   Three Months EndedSeptember 30, 2015 Three Months EndedSeptember 30, 2014 Classification Gains(Losses)onDerivatives Gains(Losses)onBorrowings  Gains(Losses)onDerivatives Gains (Losses)onBorrowingsInterest rate contractsOther income (expense) $3 $(3) $(19) $18             Nine Months EndedSeptember 30, 2015 Nine Months EndedSeptember 30, 2014 Classification Gains(Losses)onDerivatives Gains(Losses)onBorrowings  Gains(Losses)onDerivatives Gains (Losses)onBorrowingsInterest rate contractsOther income (expense) $(11) $10 $(38) $37                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
| Schedule of effect of derivatives designated as cash flow hedging instruments in the Consolidated Statements of Profit  | Cash Flow Hedges(Millions of dollars)   Three Months Ended September 30, 2015 Classification Reclassified from AOCIto Earnings(Effective Portion) Recognized in Earnings(Ineffective Portion)Interest rate contractsInterest expense $(1) $—Interest rate contractsOther income (expense) — —   $(1) $—         Three Months Ended September 30, 2014 Classification Reclassified from AOCIto Earnings(Effective Portion) Recognized in Earnings(Ineffective Portion)Interest rate contractsInterest expense $(2) $—Interest rate contractsOther income (expense) — —   $(2) $—         Nine Months Ended September 30, 2015 Classification Reclassified from AOCIto Earnings(Effective Portion) Recognized in Earnings(Ineffective Portion)Interest rate contractsInterest expense $(4) $—Interest rate contractsOther income (expense) — —   $(4) $—         Nine Months Ended September 30, 2014 Classification Reclassified from AOCIto Earnings(Effective Portion) Recognized in Earnings(Ineffective Portion)Interest rate contractsInterest expense $(4) $—Interest rate contractsOther income (expense) — —   $(4) $—       |
| Schedule of effect of derivatives not designated as hedging instruments on the Consolidated Statements of Profit        | The effect of derivatives not designated as hedging instruments on the Consolidated Statements of Profit was as follows:Undesignated Derivatives     (Millions of dollars)  Three Months Ended September 30, Classification 2015 2014Foreign exchange contractsOther income (expense) $(2) $(25)Cross currency contractsOther income (expense) 8 6   $6 $(19)         Nine Months Ended September 30, Classification 2015 2014Foreign exchange contractsOther income (expense) $(34) $(35)Cross currency contractsOther income (expense) 16 (1)   $(18) $(36)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| Schedule of offsetting of derivative assets and liabilities                                                             | The effect of net settlement provisions of the master netting agreements on our derivative balances upon an event of default or a termination event was as follows: Offsetting of Derivative Assets and Liabilities    (Millions of dollars)      September 30, 2015 December 31, 2014Derivative Assets    Gross Amount of Recognized Assets $104 $101Gross Amounts Offset — —Net Amount of Assets(1) 104 101Gross Amounts Not Offset (7) (8)Net Amount $97 $93     Derivative Liabilities    Gross Amount of Recognized Liabilities $(9) $(23)Gross Amounts Offset — —Net Amount of Liabilities(1) (9) (23)Gross Amounts Not Offset 7 8Net Amount $(2) $(15)     (1) As presented in the Consolidated Statements of Financial Position.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |

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| - Definition
Tabular disclosure of derivative and other financial assets and liabilities that are subject to offsetting, including master netting arrangements.
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| - Definition
Tabular disclosure of the effective portion of gains and losses on derivative instruments (and nonderivative instruments) designated and qualifying in cash flow hedges recorded in accumulated other comprehensive income (loss) during the term of the hedging relationship and reclassified into earnings during the current period.
+ References
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| - Definition
Tabular disclosure for cash flow hedging instruments of (a) the location and amount of gains and losses reported in the statement of financial performance and (b) the location and fair value amounts of the instruments reported in the statement of financial position.
+ References
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| - Definition
Tabular disclosure of the location and amount of derivative instruments and nonderivative instruments designated as hedging instruments reported before netting adjustments, and the amount of gain (loss) on derivative instruments and nonderivative instruments designated and qualified as hedging instruments.
+ References
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| - Definition
Tabular disclosure of the location and fair value amounts of derivative instruments (and nonderivative instruments that are designated and qualify as hedging instruments) reported in the statement of financial position.
+ References
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| - Definition
Tabular disclosure for other derivative instruments not designated as hedging instruments of (a) the location and amount of gains and losses reported in the statement of financial performance and (b) the location and fair value amounts of the instruments reported in the statement of financial position.
+ References
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