Goodwill and Intangible Assets - Finite-lived Intangible Assets Roll Forward (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 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	(3,745)	(5,466)
Total accumulated amortization	(22,965)	(17,399)
Net intangible assets, end of period	$ 12,275	$ 16,963