Goodwill and Intangible Assets - Finite-lived Intangible Assets Roll Forward (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Finite-lived Intangible Assets, Gross [Roll Forward]
Intangible assets, January 1	$ 35,240	$ 35,240
Additions	0
Total intangible assets, end of year	35,240	35,240	$ 35,240
Accumulated Amortization [Roll Forward]
Accumulated amortization, January 1	(29,985)	(27,345)
Current year amortization	(2,070)	(2,640)	(3,390)
Total accumulated amortization	(32,055)	(29,985)	$ (27,345)
Net intangible assets
Net intangible assets, end of year	3,185	5,255
Infinite-lived intangible assets	6,892	6,892
Total net intangible assets	$ 10,077	$ 12,147