as of december 31 , 2017 , the company had gross state income tax credit carry-forwards of approximately $ 20 million , which expire from 2018 through 2020 . a deferred tax asset of approximately $ 16 million ( net of federal benefit ) has been established related to these state income tax credit carry-forwards , with a valuation allowance of $ 7 million against such deferred tax asset as of december 31 , 2017 . the company had a gross state net operating loss carry-forward of $ 39 million , which expires in 2027 . a deferred tax asset of approximately $ 3 million ( net of federal benefit ) has been established for the net operating loss carry-forward , with a full valuation allowance as of december 31 , 2017 . other state and foreign net operating loss carry-forwards are separately and cumulatively immaterial to the company 2019s deferred tax balances and expire between 2026 and 2036 . 14 . debt long-term debt consisted of the following: .

1	( $ in millions )	december 31 2017	december 31 2016
2	senior notes due december 15 2021 5.000% ( 5.000 % )	2014	600
3	senior notes due november 15 2025 5.000% ( 5.000 % )	600	600
4	senior notes due december 1 2027 3.483% ( 3.483 % )	600	2014
5	mississippi economic development revenue bonds due may 1 2024 7.81% ( 7.81 % )	84	84
6	gulf opportunity zone industrial development revenue bonds due december 1 2028 4.55% ( 4.55 % )	21	21
7	less unamortized debt issuance costs	-26 ( 26 )	-27 ( 27 )
8	total long-term debt	1279	1278

credit facility - in november 2017 , the company terminated its second amended and restated credit agreement and entered into a new credit agreement ( the "credit facility" ) with third-party lenders . the credit facility includes a revolving credit facility of $ 1250 million , which may be drawn upon during a period of five years from november 22 , 2017 . the revolving credit facility includes a letter of credit subfacility of $ 500 million . the revolving credit facility has a variable interest rate on outstanding borrowings based on the london interbank offered rate ( "libor" ) plus a spread based upon the company's credit rating , which may vary between 1.125% ( 1.125 % ) and 1.500% ( 1.500 % ) . the revolving credit facility also has a commitment fee rate on the unutilized balance based on the company 2019s leverage ratio . the commitment fee rate as of december 31 , 2017 was 0.25% ( 0.25 % ) and may vary between 0.20% ( 0.20 % ) and 0.30% ( 0.30 % ) . the credit facility contains customary affirmative and negative covenants , as well as a financial covenant based on a maximum total leverage ratio . each of the company's existing and future material wholly owned domestic subsidiaries , except those that are specifically designated as unrestricted subsidiaries , are and will be guarantors under the credit facility . in july 2015 , the company used cash on hand to repay all amounts outstanding under a prior credit facility , including $ 345 million in principal amount of outstanding term loans . as of december 31 , 2017 , $ 15 million in letters of credit were issued but undrawn , and the remaining $ 1235 million of the revolving credit facility was unutilized . the company had unamortized debt issuance costs associated with its credit facilities of $ 11 million and $ 8 million as of december 31 , 2017 and 2016 , respectively . senior notes - in december 2017 , the company issued $ 600 million aggregate principal amount of unregistered 3.483% ( 3.483 % ) senior notes with registration rights due december 2027 , the net proceeds of which were used to repurchase the company's 5.000% ( 5.000 % ) senior notes due in 2021 in connection with the 2017 redemption described below . in november 2015 , the company issued $ 600 million aggregate principal amount of unregistered 5.000% ( 5.000 % ) senior notes due november 2025 , the net proceeds of which were used to repurchase the company's 7.125% ( 7.125 % ) senior notes due in 2021 in connection with the 2015 tender offer and redemption described below . interest on the company's senior notes is payable semi-annually . the terms of the 5.000% ( 5.000 % ) and 3.483% ( 3.483 % ) senior notes limit the company 2019s ability and the ability of certain of its subsidiaries to create liens , enter into sale and leaseback transactions , sell assets , and effect consolidations or mergers . the company had unamortized debt issuance costs associated with the senior notes of $ 15 million and $ 19 million as of december 31 , 2017 and 2016 , respectively. .

Question: what was the change in the unamortized debt issuance costs associated with the senior notes between 2016 and 2017?
Answer: -4