<TABLE> <S> <C>

<PAGE>
 
<ARTICLE> 5
<LEGEND>
This schedule contains summary financial information extracted from Form 10-K
for the year ended December 31, 1998 and is qualified in its entirety by
reference to such financial statements.
</LEGEND>
<MULTIPLIER> 1,000
       
<S>                                        <C>                     <C>
<PERIOD-TYPE>                                3-MOS                   12-MOS
<FISCAL-YEAR-END>                          DEC-31-1998             DEC-31-1998
<PERIOD-START>                             OCT-01-1998             JAN-01-1998
<PERIOD-END>                               DEC-31-1998             DEC-31-1998
<CASH>                                          30,604                  30,604
<SECURITIES>                                         0                       0
<RECEIVABLES>                                  173,924                 173,924
<ALLOWANCES>                                    (7,872)                 (7,872)
<INVENTORY>                                          0                       0
<CURRENT-ASSETS>                                     0                       0
<PP&E>                                       3,702,341               3,702,341
<DEPRECIATION>                              (1,050,129)             (1,050,129)
<TOTAL-ASSETS>                              12,878,104              12,878,104
<CURRENT-LIABILITIES>                                0                       0
<BONDS>                                              0                       0
<PREFERRED-MANDATORY>                         (277,355)               (277,355)
<PREFERRED>                                          0                       0
<COMMON>                                        (2,418)                 (2,418)
<OTHER-SE>                                           0                       0
<TOTAL-LIABILITY-AND-EQUITY>               (12,878,104)            (12,878,104)
<SALES>                                              0                       0
<TOTAL-REVENUES>                              (486,705)             (1,716,757)
<CGS>                                                0                       0
<TOTAL-COSTS>                                  150,162                 539,499
<OTHER-EXPENSES>                               145,295                 457,671
<LOSS-PROVISION>                                     0                       0
<INTEREST-EXPENSE>                              70,525                 223,326
<INCOME-PRETAX>                                528,264               2,093,487
<INCOME-TAX>                                   210,401                 822,815
<INCOME-CONTINUING>                            317,863               1,270,672
<DISCONTINUED>                                       0                       0
<EXTRAORDINARY>                                      0                       0
<CHANGES>                                            0                       0
<NET-INCOME>                                   317,863               1,270,672
<EPS-PRIMARY>                                     1.15                    4.66
<EPS-DILUTED>                                     1.13                    4.60
        

</TABLE>