INCOME TAXES - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Minimum tax credit	$ 0	$ 64,203
Insurance and other accruals	1,455	3,151
Compensation accruals	6,645	13,895
Deferred compensation and other costs	2,605	5,401
Derivative instruments	16,032	22,402
Federal net operating losses and other carryforwards	2,350	0
State net operating losses and other carryforwards	15,642	12,947
Other	338	535
Total deferred tax assets	45,067	122,534
Valuation allowance	(7,710)	(5,735)
Total deferred tax assets	37,357	116,799
Deferred tax liabilities:
Depreciation and basis differences	417,376	603,324
Other comprehensive income	223	854
Other	7,565	8,509
Total deferred tax liabilities	425,164	612,687
Net deferred tax liabilities	$ (387,807)	$ (495,888)