Fair Value Measurements (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
Fair value of notes payable	$ 1,089,500		$ 1,090,000
Assets at fair value	2,500		$ 1,100
Increase in interest expense	400
Change in fair value recorded in earnings	69
Interest rate contracts
Derivative, Notional Amount	$ 100,000	$ 100,000