Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Treasury Stock	Additional Paid-In Capital	Retained Deficit	Accum. Other Comp. Loss	Total CVG Stockholders’ Equity
Beginning Balance (in shares) at Dec. 31, 2016		29,871,354
Beginning balance at Dec. 31, 2016	$ 65,835	$ 299	$ (7,753)	$ 237,367	$ (115,233)	$ (48,845)	$ 65,835
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of restricted stock (in shares)		509,306
Issuance of restricted stock		$ 5					5
Surrender of common stock by employees (in shares)		(161,382)
Surrender of common stock by employees			(1,361)				(1,361)
Share-based compensation expense				2,503			2,503
Total comprehensive income	5,341				(2,269)	7,610	5,341
Ending balance (in shares) at Dec. 31, 2017		30,219,278
Ending balance at Dec. 31, 2017	72,323	$ 304	(9,114)	239,870	(117,502)	(41,235)	72,323
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total comprehensive income	10,576					1,132
Ending balance (in shares) at Mar. 31, 2018		30,219,000
Ending balance at Mar. 31, 2018	83,572	$ 304	(9,114)	240,543	(108,058)	(40,103)
Beginning Balance (in shares) at Dec. 31, 2017		30,219,278
Beginning balance at Dec. 31, 2017	72,323	$ 304	(9,114)	239,870	(117,502)	(41,235)	72,323
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total comprehensive income	17,349
Ending balance (in shares) at Jun. 30, 2018		30,219,000
Ending balance at Jun. 30, 2018	91,189	$ 304	(9,114)	241,387	(95,387)	(46,001)
Beginning Balance (in shares) at Dec. 31, 2017		30,219,278
Beginning balance at Dec. 31, 2017	72,323	$ 304	(9,114)	239,870	(117,502)	(41,235)	72,323
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total comprehensive income	26,037
Ending balance (in shares) at Sep. 30, 2018		30,219,000
Ending balance at Sep. 30, 2018	100,657	$ 304	(9,114)	242,167	(84,110)	(48,590)
Beginning Balance (in shares) at Dec. 31, 2017		30,219,278
Beginning balance at Dec. 31, 2017	72,323	$ 304	(9,114)	239,870	(117,502)	(41,235)	72,323
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of restricted stock (in shares)		452,021
Issuance of restricted stock		$ 14					14
Surrender of common stock by employees (in shares)		(158,456)
Surrender of common stock by employees			(1,131)				(1,131)
Share-based compensation expense				3,137			3,137
Total comprehensive income	$ 35,253				41,489	(6,236)	35,253
Ending balance (in shares) at Dec. 31, 2018	30,512,843	30,512,843
Ending balance at Dec. 31, 2018	$ 109,596	$ 318	(10,245)	243,007	(76,013)	(47,471)	109,596
Beginning Balance (in shares) at Mar. 31, 2018		30,219,000
Beginning balance at Mar. 31, 2018	83,572	$ 304	(9,114)	240,543	(108,058)	(40,103)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total comprehensive income	6,773				12,671	(5,898)
Ending balance (in shares) at Jun. 30, 2018		30,219,000
Ending balance at Jun. 30, 2018	91,189	$ 304	(9,114)	241,387	(95,387)	(46,001)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total comprehensive income	8,688				11,277	(2,589)
Ending balance (in shares) at Sep. 30, 2018		30,219,000
Ending balance at Sep. 30, 2018	100,657	$ 304	(9,114)	242,167	(84,110)	(48,590)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of restricted stock (in shares)		452,000
Issuance of restricted stock	14	$ 14
Surrender of common stock by employees (in shares)		(158,000)
Surrender of common stock by employees	(1,131)		(1,131)
Total comprehensive income	$ 9,216				8,097	1,119
Ending balance (in shares) at Dec. 31, 2018	30,512,843	30,512,843
Ending balance at Dec. 31, 2018	$ 109,596	$ 318	(10,245)	243,007	(76,013)	(47,471)	109,596
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total comprehensive income	9,780				9,986	(206)
Ending balance (in shares) at Mar. 31, 2019		30,513,000
Ending balance at Mar. 31, 2019	$ 120,065	$ 318	(10,245)	243,768	(66,099)	(47,677)
Beginning Balance (in shares) at Dec. 31, 2018	30,512,843	30,512,843
Beginning balance at Dec. 31, 2018	$ 109,596	$ 318	(10,245)	243,007	(76,013)	(47,471)	109,596
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total comprehensive income	17,881
Ending balance (in shares) at Jun. 30, 2019		30,581,000
Ending balance at Jun. 30, 2019	$ 128,885	$ 319	(10,245)	244,486	(59,953)	(45,722)
Beginning Balance (in shares) at Dec. 31, 2018	30,512,843	30,512,843
Beginning balance at Dec. 31, 2018	$ 109,596	$ 318	(10,245)	243,007	(76,013)	(47,471)	109,596
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total comprehensive income	19,063
Ending balance (in shares) at Sep. 30, 2019		30,581,000
Ending balance at Sep. 30, 2019	$ 130,788	$ 319	(10,245)	245,207	(52,773)	(51,720)
Beginning Balance (in shares) at Dec. 31, 2018	30,512,843	30,512,843
Beginning balance at Dec. 31, 2018	$ 109,596	$ 318	(10,245)	243,007	(76,013)	(47,471)	109,596
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of restricted stock (in shares)		418,553
Issuance of restricted stock		$ 5					5
Surrender of common stock by employees (in shares)		(130,141)
Surrender of common stock by employees			(985)				(985)
Share-based compensation expense				2,845			2,845
Total comprehensive income	$ 17,299				15,778		17,299
Ending balance (in shares) at Dec. 31, 2019	30,801,255	30,801,255
Ending balance at Dec. 31, 2019	$ 128,688	$ 323	(11,230)	245,852	(60,307)	(45,950)	128,688
Beginning Balance (in shares) at Mar. 31, 2019		30,513,000
Beginning balance at Mar. 31, 2019	120,065	$ 318	(10,245)	243,768	(66,099)	(47,677)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total comprehensive income	8,101				6,146	1,955
Ending balance (in shares) at Jun. 30, 2019		30,581,000
Ending balance at Jun. 30, 2019	128,885	$ 319	(10,245)	244,486	(59,953)	(45,722)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total comprehensive income	1,182				7,180	(5,998)
Ending balance (in shares) at Sep. 30, 2019		30,581,000
Ending balance at Sep. 30, 2019	130,788	$ 319	(10,245)	245,207	(52,773)	(51,720)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of restricted stock (in shares)		351,000
Issuance of restricted stock	4	$ 4
Surrender of common stock by employees (in shares)		(131,000)
Surrender of common stock by employees	(985)		(985)
Total comprehensive income	$ (1,764)				(7,534)	5,770
Ending balance (in shares) at Dec. 31, 2019	30,801,255	30,801,255
Ending balance at Dec. 31, 2019	$ 128,688	$ 323	$ (11,230)	$ 245,852	$ (60,307)	$ (45,950)	$ 128,688