Notes Payable, Revolving Credit Facility, Interest and Amortization of Deferred Debt Costs - Interest Expense and Amortization of Deferred Debt Costs (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Debt Disclosure [Abstract]
Interest incurred	$ 12,370	$ 11,691	$ 37,037	$ 35,027
Amortization of deferred debt costs	351	339	1,043	1,003
Capitalized interest	(900)	(506)	(2,495)	(1,762)
Interest expense and amortization of deferred debt costs	$ 11,821	$ 11,524	$ 35,585	$ 34,268