Goodwill and Intangible Assets - Finite-lived Intangible Assets Roll Forward (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Finite-lived Intangible Assets, Gross [Roll Forward]
Intangible assets, January 1	$ 34,362	$ 34,362
Additions	878	0
Total intangible assets, end of period	35,240	34,362
Accumulated amortization, January 1
Accumulated amortization, January 1	(19,220)	(11,933)
Current year amortization	(2,613)	(1,822)
Total accumulated amortization	(21,833)	(13,755)
Net intangible assets, end of period	$ 13,407	$ 20,607