Interest and Debt Expense - Details of Interest and Debt Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Interest And Debt Expense [Abstract]
Interest expense	$ 34,353	$ 32,914	$ 101,729	$ 99,201
Amortization of deferred financing costs	2,752	2,819	8,267	8,367
Total interest and debt expense	$ 37,105	$ 35,733	$ 109,996	$ 107,568