Cumulative Other Comprehensive Loss - Schedule of Amounts Recognized in Cumulative Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2018
Amounts recognized in cumulative other comprehensive income (Loss) by component
Balance as of beginning of period		$ 3,300,495
Amounts reclassified from cumulative other comprehensive loss to cumulative net income pursuant to a change in accounting principle		(1,902)
Other comprehensive income before reclassifications		619
Amounts reclassified from cumulative other comprehensive [loss] to net income [(loss)]		372
Net current period other comprehensive income		991
Balance as of end of period	$ 3,169,511	3,169,511
Unrealized Loss on Derivative Instruments
Amounts recognized in cumulative other comprehensive income (Loss) by component
Balance as of beginning of period		(456)
Amounts reclassified from cumulative other comprehensive loss to cumulative net income pursuant to a change in accounting principle		0
Other comprehensive income before reclassifications		84
Amounts reclassified from cumulative other comprehensive [loss] to net income [(loss)]		372
Net current period other comprehensive income		456
Balance as of end of period	0	0
Unrealized Gain (Loss) on Marketable Securities
Amounts recognized in cumulative other comprehensive income (Loss) by component
Balance as of beginning of period	(1,469)	361
Amounts reclassified from cumulative other comprehensive loss to cumulative net income pursuant to a change in accounting principle		(1,902)
Other comprehensive income before reclassifications	463	535
Amounts reclassified from cumulative other comprehensive [loss] to net income [(loss)]		0
Net current period other comprehensive income	463	535
Balance as of end of period	(1,006)	(1,006)
AOCI Including Portion Attributable to Noncontrolling Interest
Amounts recognized in cumulative other comprehensive income (Loss) by component
Balance as of beginning of period		(95)
Balance as of end of period	$ (1,006)	$ (1,006)