Fair Value Measurements (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Fair value of notes payable	$ 1,348,100,000	$ 1,090,000,000
Assets at fair value	1,700,000	1,100,000
Change in fair value recorded in earnings	(400,000)	600,000	$ 25,000
Interest rate contract
Derivative, Notional Amount	$ 100,000,000	$ 100,000,000