Debt Facilities - Interest Charges (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Debt Disclosure [Abstract]
Interest expense	$ 134,673	$ 119,042	$ 260,950	$ 230,726
Interest capitalized	3,484	7,999	6,798	14,399
Interest charges incurred	138,157	127,041	267,748	245,125
Interest paid, net of capitalized interest	$ 111,600	$ 90,000	$ 215,300	$ 199,000