Notes Payable - Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Interest incurred and expensed
Interest expense on debt and capital lease obligations	$ 11,479	$ 11,499	$ 22,745	$ 22,827
Noncash interest on derivatives and capital lease obligations, net	(1,040)	1,006	(4,177)	349
Amortization of deferred financing fees	745	579	1,492	1,157
Total interest incurred and expensed on debt and capital lease obligations	$ 11,184	$ 13,084	$ 20,060	$ 24,333