Derivative Instruments and Hedging Activities - Interest Rate Derivatives Designated as Cash Flow Hedges (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
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	$ (69,366)	$ (42,187)	$ (129,263)	$ (78,774)
Amount of gain recognized in other comprehensive (loss) income	637	(1,482)	3,388	(1,265)
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	$ (866)	$ (2,314)	$ (2,317)	$ (4,832)