Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 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	18,098
Amounts reclassified from accumulated other comprehensive income	(403)
Ending Balance	6,267,175
Deferred net losses from terminated hedges	1,800	$ 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	11,876
Amounts reclassified from accumulated other comprehensive income	(36)
Ending Balance	24,382
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	(44)
Amounts reclassified from accumulated other comprehensive income	0
Ending Balance	998
Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) of the Company [Roll Forward]
Beginning Balance	18,604
Ending Balance	36,299
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	6,266
Amounts reclassified from accumulated other comprehensive income	(367)
Ending Balance	$ 10,919