Income Taxes - Income Tax Contingencies (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income tax contingency disclosures
Unrecognized tax benefits: Changes due to lapses of statutes of limitations		$ 2,693	$ 2,235	$ 3,071
Accrued interest and penalties related to unrecognized tax benefits		500	300
Interest and penalties recorded		200	100	(400)
Forecast
Income tax contingency disclosures
Unrecognized tax benefits: Changes due to lapses of statutes of limitations	$ 2,900
Deferred tax assets
Income tax contingency disclosures
Unrecognized tax benefits: Changes due to lapses of statutes of limitations		1,000	700	1,000
Deferred tax assets | Forecast
Income tax contingency disclosures
Unrecognized tax benefits: Changes due to lapses of statutes of limitations	600
Income Tax Expense
Income tax contingency disclosures
Unrecognized tax benefits: Changes due to lapses of statutes of limitations		2,000	1,500	2,000
Interest expense related to unrecognized tax benefits		$ (200)	$ (100)	(400)
Income Tax Expense | Forecast
Income tax contingency disclosures
Unrecognized tax benefits: Changes due to lapses of statutes of limitations	$ 2,300
Income Tax Expense | State
Income tax contingency disclosures
Unrecognized tax benefits: Changes due to lapses of statutes of limitations				$ 700