Interest and Debt Expense - Details of Interest and Debt Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Interest And Debt Expense [Abstract]
Interest expense	$ 34,055	$ 31,999	$ 67,376	$ 66,287
Amortization of deferred financing costs	2,754	2,818	5,515	5,548
Total interest and debt expense	$ 36,809	$ 34,817	$ 72,891	$ 71,835