Debt Facilities - Interest Charges (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Debt Disclosure [Abstract]
Interest expense	$ 130,566	$ 121,828	$ 391,516	$ 352,554
Interest capitalized	6,206	6,174	13,004	20,573
Interest charges incurred	136,772	128,002	404,520	373,127
Interest paid, net of capitalized interest	$ 146,700	$ 122,800	$ 362,000	$ 321,800