Revenue Recognition - Impact of ASC 606 Adoption (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Assets
Other non-current assets	$ 2,139		$ 1,636
Liabilities
Deferred income taxes	12,208		12,043
Stockholder's equity
Retained earnings	123,393		124,442
Operating expenses
Selling, general and administrative expenses	61,167	$ 53,615
Income from operations	1,241	9,225
Income (loss) before taxes	(1,111)	8,032
Income tax expense	573	2,354
Net (loss) income	$ (1,684)	$ 5,678
Basic earnings (loss) per share (in dollars per share)	$ (0.03)	$ 0.11
Diluted earnings (loss) per share (in dollars per share)	$ (0.03)	$ 0.10
Adjustments
Assets
Other non-current assets	$ (623)
Liabilities
Deferred income taxes	167
Stockholder's equity
Retained earnings	(456)
Operating expenses
Selling, general and administrative expenses	(26)
Income from operations	26
Income (loss) before taxes	26
Income tax expense	6
Net (loss) income	$ 20
Basic earnings (loss) per share (in dollars per share)	$ 0.00
Diluted earnings (loss) per share (in dollars per share)	$ 0.00
As Adjusted Without Adoption of ASC 606
Assets
Other non-current assets	$ 1,516
Liabilities
Deferred income taxes	12,375
Stockholder's equity
Retained earnings	122,937
Operating expenses
Selling, general and administrative expenses	61,141
Income from operations	1,267
Income (loss) before taxes	(1,085)
Income tax expense	579
Net (loss) income	$ (1,664)
Basic earnings (loss) per share (in dollars per share)	$ (0.03)
Diluted earnings (loss) per share (in dollars per share)	$ (0.03)
Accounting Standards Update 2014-09
Stockholder's equity
Retained earnings			$ 500