Notes Payable (Other Information) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Debt Disclosure [Abstract]
Total interest incurred	$ 11,103	$ 10,741	$ 21,977	$ 22,072
Interest capitalized	(1,389)	(2,218)	(2,485)	(3,808)
Total interest expense	$ 9,714	$ 8,523	$ 19,492	$ 18,264