Notes Payable (Other Information) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Debt Disclosure [Abstract]
Total interest incurred	$ 11,087	$ 10,288	$ 33,064	$ 32,360
Interest capitalized	(1,536)	(2,701)	(4,021)	(6,509)
Total interest expense	$ 9,551	$ 7,587	$ 29,043	$ 25,851