Goodwill and Other Intangible Assets - Intangibles (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
GOODWILL AND OTHER INTANGIBLE ASSETS
Definite-lived, Gross Carrying Amount	$ 37,318		$ 37,318		$ 35,682
Definite-lived, Accumulated Amortization	(25,665)		(25,665)		(24,321)
Definite-lived, Net Carrying Amount	11,653		11,653		11,361
Total other intangible assets, Gross Carrying Amount	46,388		46,388		44,752
Total other intangible assets, Accumulated Impairment	(4,953)		(4,953)		(4,953)
Total other intangible assets, Net Carrying Amount	15,770		15,770		15,478
Amortization expense	1,100	$ 1,800	2,400	$ 3,800
Trade name
GOODWILL AND OTHER INTANGIBLE ASSETS
Indefinite lived, Gross Carrying Amount	9,070		9,070		9,070
Indefinite lived, Accumulated Impairment	(4,953)		(4,953)		(4,953)
Indefinite lived, Net Carrying Amount	4,117		4,117		4,117
Customer lists
GOODWILL AND OTHER INTANGIBLE ASSETS
Definite-lived, Gross Carrying Amount	27,825		27,825		26,036
Definite-lived, Accumulated Amortization	(20,311)		(20,311)		(19,051)
Definite-lived, Net Carrying Amount	7,514		7,514		6,985
Trade name
GOODWILL AND OTHER INTANGIBLE ASSETS
Definite-lived, Gross Carrying Amount	255		255		255
Definite-lived, Accumulated Amortization	(138)		(138)		(125)
Definite-lived, Net Carrying Amount	117		117		130
Patents and other intangibles
GOODWILL AND OTHER INTANGIBLE ASSETS
Definite-lived, Gross Carrying Amount	9,238		9,238		9,391
Definite-lived, Accumulated Amortization	(5,216)		(5,216)		(5,145)
Definite-lived, Net Carrying Amount	$ 4,022		$ 4,022		$ 4,246