CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Traditional Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning balance at Dec. 31, 2017	$ 100,440	$ 73	$ 243,598	$ 232	$ (143,463)
Beginning balance (in shares) at Dec. 31, 2017		7,303
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income after equity in losses of unconsolidated affiliates	4,052
Ending balance at Jun. 30, 2018	109,922	$ 75	246,422	201	(136,776)
Ending balance (in shares) at Jun. 30, 2018		7,498
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption of accounting standards	2,635				2,635
Beginning balance at Jan. 01, 2018	103,075	$ 73	243,598	232	(140,828)
Beginning balance (in shares) at Jan. 01, 2018		7,303
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income after equity in losses of unconsolidated affiliates	4,052				4,052
Issuance of common stock, net of shares withheld for employee taxes	458	$ 2	456
Issuance of common stock, net of shares withheld for employee taxes (in shares)		195
Stock-based compensation	2,368		2,368
Other comprehensive income (loss)	(31)			(31)
Ending balance at Jun. 30, 2018	109,922	$ 75	246,422	201	(136,776)
Ending balance (in shares) at Jun. 30, 2018		7,498
Beginning balance at Mar. 31, 2018	105,091	$ 74	243,377	313	(138,673)
Beginning balance (in shares) at Mar. 31, 2018		7,419
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income after equity in losses of unconsolidated affiliates	1,897				1,897
Issuance of common stock, net of shares withheld for employee taxes	1,742	$ 1	1,741
Issuance of common stock, net of shares withheld for employee taxes (in shares)		79
Stock-based compensation	1,304		1,304
Other comprehensive income (loss)	(112)			(112)
Ending balance at Jun. 30, 2018	109,922	$ 75	246,422	201	(136,776)
Ending balance (in shares) at Jun. 30, 2018		7,498
Beginning balance at Dec. 31, 2018	122,409	$ 77	257,034	277	(134,979)
Beginning balance (in shares) at Dec. 31, 2018		7,676
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income after equity in losses of unconsolidated affiliates	573				573
Issuance of common stock, net of shares withheld for employee taxes	(2,461)	$ 1	(2,462)
Issuance of common stock, net of shares withheld for employee taxes (in shares)		118
Stock-based compensation	2,380		2,380
Other comprehensive income (loss)	21			21
Ending balance at Jun. 30, 2019	122,922	$ 78	256,952	298	(134,406)
Ending balance (in shares) at Jun. 30, 2019		7,794
Beginning balance at Mar. 31, 2019	121,277	$ 77	255,150	215	(134,165)
Beginning balance (in shares) at Mar. 31, 2019		7,747
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income after equity in losses of unconsolidated affiliates	(241)				(241)
Issuance of common stock, net of shares withheld for employee taxes	608	$ 1	607
Issuance of common stock, net of shares withheld for employee taxes (in shares)		47
Stock-based compensation	1,195		1,195
Other comprehensive income (loss)	83			83
Ending balance at Jun. 30, 2019	$ 122,922	$ 78	$ 256,952	$ 298	$ (134,406)
Ending balance (in shares) at Jun. 30, 2019		7,794