Restatement and Revision of Previously Issued Consolidated Financial Statements - Consolidated Statements of Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended								6 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating activities
Income (loss) from continuing operations, net of tax	$ 13,304	$ 553	$ 1,898	$ (662)	$ 11,490	$ 9,030	$ 1,645	$ 894	$ 1,236	$ 2,539	$ 1,789	$ 11,569	$ 15,093	$ 23,059	$ 18,109
Adjustments to reconcile net income from continuing operations to net cash provided by operating activities:
Depreciation and amortization													4,002	4,277	4,072
Deferred income taxes													1,487	5,474	3,475
Stock compensation expense													2,797	3,618	323
Other													616	837	(1,167)
Net changes in operating assets and liabilities:
Affiliate payable													(1,920)	(5,300)	866
Trade receivables													(22,769)	18,529	(8,128)
Inventory													13,674	(12,255)	(16,566)
Other assets													1,127	(4,586)	(1,295)
Accounts payable													(7,043)	(7,719)	25,009
Other liabilities													(6,842)	(7,979)	3,605
Net cash provided by operating activities from continuing operations													222	17,955	28,303
Investing activities
Expenditures for property, plant and equipment													(4,122)	(7,759)	(6,198)
Other													0	0	21
Net cash used for investing activities from continuing operations													(4,122)	(7,759)	(6,177)
Financing activities
Net additions (reductions) to revolving credit agreements													11,873	(4,597)	12,630
Purchase of treasury stock													(5,960)	0	0
Cash dividends paid													0	0	(38,000)
Net cash provided by (used for) financing activities from continuing operations													1,062	(9,255)	(26,532)
Cash flows from discontinued operations
Net cash provided by (used for) operating activities from discontinued operations													3,953	(5,499)	5,137
Net cash provided by (used for) investing activities from discontinued operations													585	(305)	(1,176)
Net cash used for financing activities from discontinued operations													(103)	0	(70)
Cash provided by (used for) discontinued operations													4,435	(5,804)	3,891
Effect of exchange rate changes on cash													(785)	309	81
Cash, cash equivalents and restricted cash
(Decrease) increase for the year from continuing operations													(3,623)	1,250	(4,325)
Increase (decrease) for the year from discontinued operations													4,435	(5,804)	3,891
Balance at the beginning of the year				6,352				10,906	6,352	10,906	6,352	10,906	6,352	10,906	11,340
Balance at the end of the year	7,164				6,352								7,164	6,352	10,906
As Previously Reported
Operating activities
Income (loss) from continuing operations, net of tax	19,394	397	(944)	(1,761)	12,661	8,044	(874)	(418)	(2,705)	(1,292)	(2,308)	6,752	25,078	27,145	20,130
Adjustments to reconcile net income from continuing operations to net cash provided by operating activities:
Depreciation and amortization													4,002	4,277	4,072
Deferred income taxes													3,248	5,185	4,107
Stock compensation expense													2,632	3,618	323
Other													471	868	(1,167)
Net changes in operating assets and liabilities:
Affiliate payable													(1,920)	(5,300)	866
Trade receivables													(25,586)	16,298	(8,442)
Inventory													13,756	(12,308)	(16,485)
Other assets													(3,121)	(10,509)	(1,960)
Accounts payable													(7,257)	(7,756)	25,009
Other liabilities													(11,101)	(4,195)	1,850
Net cash provided by operating activities from continuing operations													202	17,323	28,303
Investing activities
Expenditures for property, plant and equipment													(4,122)	(7,759)	(6,198)
Other													0	0	21
Net cash used for investing activities from continuing operations													(4,122)	(7,759)	(6,177)
Financing activities
Net additions (reductions) to revolving credit agreements													11,873	(4,597)	12,630
Purchase of treasury stock													(5,960)	0	0
Cash dividends paid													0	0	(38,000)
Net cash provided by (used for) financing activities from continuing operations													1,062	(9,255)	(26,532)
Cash flows from discontinued operations
Net cash provided by (used for) operating activities from discontinued operations													3,953	(5,499)	5,137
Net cash provided by (used for) investing activities from discontinued operations													585	(305)	(1,176)
Net cash used for financing activities from discontinued operations													(103)	0	(70)
Cash provided by (used for) discontinued operations													4,435	(5,804)	3,891
Effect of exchange rate changes on cash													(765)	941	81
Cash, cash equivalents and restricted cash
(Decrease) increase for the year from continuing operations													(3,623)	1,250	(4,325)
Increase (decrease) for the year from discontinued operations													4,435	(5,804)	3,891
Balance at the beginning of the year				6,352				10,906	6,352	10,906	6,352	10,906	6,352	10,906	11,340
Balance at the end of the year	7,164				6,352								7,164	6,352	10,906
Restatement Impacts
Operating activities
Income (loss) from continuing operations, net of tax	(6,090)	$ (2,597)	$ 326	(1,624)	(1,171)	$ (903)	$ (247)	(1,765)	(1,298)	(2,012)	(3,895)	(2,915)	(9,985)	(4,086)	(2,021)
Adjustments to reconcile net income from continuing operations to net cash provided by operating activities:
Depreciation and amortization													0	0	0
Deferred income taxes													(1,761)	289	(632)
Stock compensation expense													165	0	0
Other													145	(31)	0
Net changes in operating assets and liabilities:
Affiliate payable													0	0	0
Trade receivables													2,817	2,231	314
Inventory													(82)	53	(81)
Other assets													4,248	5,923	665
Accounts payable													214	37	0
Other liabilities													4,259	(3,784)	1,755
Net cash provided by operating activities from continuing operations													20	632	0
Investing activities
Expenditures for property, plant and equipment													0	0	0
Other													0	0	0
Net cash used for investing activities from continuing operations													0	0	0
Financing activities
Net additions (reductions) to revolving credit agreements													0	0	0
Purchase of treasury stock													0	0	0
Cash dividends paid													0	0	0
Net cash provided by (used for) financing activities from continuing operations													0	0	0
Cash flows from discontinued operations
Net cash provided by (used for) operating activities from discontinued operations													0	0	0
Net cash provided by (used for) investing activities from discontinued operations													0	0	0
Net cash used for financing activities from discontinued operations													0	0	0
Cash provided by (used for) discontinued operations													0	0	0
Effect of exchange rate changes on cash													(20)	(632)	0
Cash, cash equivalents and restricted cash
(Decrease) increase for the year from continuing operations													0	0	0
Increase (decrease) for the year from discontinued operations													0	0	0
Balance at the beginning of the year				$ 0				$ 0	$ 0	$ 0	$ 0	$ 0	0	0	0
Balance at the end of the year	$ 0				$ 0								0	0	0
Common Class A and B
Financing activities
Cash dividends paid													(4,851)	(4,658)	(1,162)
Common Class A and B | As Previously Reported
Financing activities
Cash dividends paid													(4,851)	(4,658)	(1,162)
Common Class A and B | Restatement Impacts
Financing activities
Cash dividends paid													$ 0	$ 0	$ 0