Revenue Recognition - Effect on Financial Statements (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2018
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Other current assets	$ 3,121	$ 4,335		$ 4,098
Intangible, equity method investment and other assets, net	5,048	6,520		20,792
Deferred income tax liability, net	12,381	12,886
Accumulated deficit	(7,589)	(11,337)		$ (11,731)
Selling, general and administrative expenses	62,572	60,463	$ 59,224
Income tax provision	1,287	(5,482)	14
Net income	4,142	9,523	$ (320)
Balance without Adoption of ASC 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Other current assets	3,279	4,335
Intangible, equity method investment and other assets, net		20,949
Deferred income tax liability, net	12,437
Accumulated deficit	(7,803)	(11,337)
Selling, general and administrative expenses	62,809
Income tax provision	1,231
Net income	3,961
Adjustments due to ASC 606 | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Other current assets	(158)	(237)
Intangible, equity method investment and other assets, net		(157)
Deferred income tax liability, net	(56)
Accumulated deficit	(214)	$ (394)
Selling, general and administrative expenses	(237)
Income tax provision	56
Net income	$ 181