Summary of Significant Accounting Policies - Reclassifications (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Interest expense	$ 24,196	$ 22,873	$ 24,048
Loss on the extinguishment of debt	$ 11,883	326	1,208
Reclassification
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Interest expense		(300)	(1,200)
Loss on the extinguishment of debt		$ 300	$ 1,200