Goodwill and Intangible Assets - Finite-lived Intangible Assets Roll Forward (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Finite-lived intangible assets, gross
Finite-lived intangible assets, January 1			$ 35,240	$ 35,240	$ 35,240
Additions			0		0
Total finite-lived intangible assets, end of period	$ 35,240		35,240		35,240
Accumulated amortization
Accumulated amortization, January 1			(27,345)	(23,956)	(23,956)
Current year amortization	(662)	$ (847)	(1,980)	$ (2,541)	(3,389)
Total accumulated amortization	(29,325)		(29,325)		(27,345)
Net intangible assets
Net finite-lived intangible assets, end of period	5,915		5,915		7,895
Infinite-lived intangible assets	6,892		6,892		6,892
Total net intangible assets	$ 12,807		$ 12,807		$ 14,787