Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 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	13,920
Amounts reclassified from accumulated other comprehensive income	98
Ending Balance	6,242,056
Deferred net losses from terminated hedges	2,200	$ 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	9,837
Amounts reclassified from accumulated other comprehensive income	237
Ending Balance	22,616
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	(14)
Amounts reclassified from accumulated other comprehensive income	0
Ending Balance	1,028
Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) of the Company [Roll Forward]
Beginning Balance	18,604
Ending Balance	32,622
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	4,097
Amounts reclassified from accumulated other comprehensive income	(139)
Ending Balance	$ 8,978