Derivative Instruments and Hedging Activities - Interest Rate Derivatives Designated as Cash Flow Hedges (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Amounts Related To Interest Rate Derivatives Included In Income Designated As Hedges Of Cash Flows [Line Items]
Amount of loss reclassified from accumulated other comprehensive loss to interest expense	$ (46,796)	$ (37,057)	$ (125,570)	$ (112,074)
Amount of gain (loss) recognized in other comprehensive income	329	2,962	(936)	(11,695)
Reclassification Out of Accumulated Other Comprehensive Income (Loss)
Amounts Related To Interest Rate Derivatives Included In Income Designated As Hedges Of Cash Flows [Line Items]
Amount of loss reclassified from accumulated other comprehensive loss to interest expense	$ (1,930)	$ (3,578)	$ (6,762)	$ (10,146)