Debt - Interest Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Debt Disclosure [Abstract]
Gross interest expense	$ 328,228	$ 383,098	$ 394,012
Amortization of premium, net	(13,728)	(30,596)	(45,253)
Amortization of debt issuance costs	14,479	15,459	13,412
Interest expense before capitalization	328,979	367,961	362,171
Capitalized amounts	(54,493)	(64,815)	(60,808)
Net interest expense	274,486	303,146	301,363
Total cash paid for interest, net of amounts capitalized	$ 278,313	$ 322,442	$ 345,916