Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) of the Company [Roll Forward]
Beginning Balance	$ 6,589,454
Other comprehensive (loss) income before reclassifications	9,658
Amounts reclassified from accumulated other comprehensive income	311
Ending Balance	6,537,629
Deferred net losses from terminated hedges	2,700	$ 3,200
Net unrealized (loss) gain on derivative instruments
Accumulated Other Comprehensive Income (Loss) of the Company [Roll Forward]
Beginning Balance	12,542
Other comprehensive (loss) income before reclassifications	6,859
Amounts reclassified from accumulated other comprehensive income	310
Ending Balance	19,711
Net unrealized gain on marketable securities
Accumulated Other Comprehensive Income (Loss) of the Company [Roll Forward]
Beginning Balance	1,042
Other comprehensive (loss) income before reclassifications	(315)
Amounts reclassified from accumulated other comprehensive income	0
Ending Balance	727
Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) of the Company [Roll Forward]
Beginning Balance	18,604
Ending Balance	28,573
Joint venture | Net unrealized (loss) gain on derivative instruments
Accumulated Other Comprehensive Income (Loss) of the Company [Roll Forward]
Beginning Balance	5,020
Other comprehensive (loss) income before reclassifications	3,114
Amounts reclassified from accumulated other comprehensive income	1
Ending Balance	$ 8,135