Income Taxes (Effective tax rate reconciliation) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Difference between the Federal corporate tax rate and the effective tax rate
Income tax provision computed at US federal statutory rate	$ 1,974	$ 7,657	$ 11,859
Canadian rate differential	(26)	895	(1,398)
Change in ASC 740-10 positions (net)	512	916	626
Other, net	408	521	421
Income tax expense (benefit)	$ 3,491	$ 9,711	$ 13,904
Income tax provision computed at US federal statutory rate, effective tax rate	21.00%	21.00%	35.00%
Canadian rate differential, effective tax rate	(0.30%)	2.40%	(4.10%)
Global Intangible Low Taxed Income, Net Deductions	$ 0	$ 1,573	$ 0
Global Intangible Low Taxed Income, Percent	0.00%	4.30%	0.00%
State and local income taxes, net of federal income taxes, effective tax rate	5.40%	2.50%	1.90%
Effective Income Tax Rate Reconciliation, Tax Credit, Amount	$ 0	$ 1,528	$ 0
Effective Income Tax Rate Reconciliation, Tax Credit, Percent	0.00%	4.20%	0.00%
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount	$ 30	$ (10)	$ 1,578
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Percent	0.30%	0.00%	4.60%
Effective Income Tax Rate Reconciliation, Repatriation of Foreign Earnings, Amount	$ 0	$ 118	$ 1,767
Effective Income Tax Rate Reconciliation, Repatriation of Foreign Earnings, Percent	0.00%	0.30%	5.20%
Other, net, effective tax rate	4.40%	1.40%	1.20%
Effective income tax rate	37.10%	26.60%	41.00%
State and local income taxes, net of federal income taxes, effective tax rate	5.40%	2.50%	1.90%
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	$ 3,975	$ 0	$ 0
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Share-based Payment Arrangement, Amount	$ 594	$ (450)	$ (946)
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Share-based Payment Arrangement, Percent	6.30%	(1.20%)	(2.80%)
Effective Income Tax Rate Reconciliation, Tax Contingency, Amount [Abstract]
Effective Income Tax Rate Reconciliation, Tax Contingency, State and Local, Percent	0.00%	0.10%	0.00%
Income tax provision computed at US federal statutory rate, effective tax rate	21.00%	21.00%	35.00%
Canadian rate differential, effective tax rate	(0.30%)	2.40%	(4.10%)
Global Intangible Low Taxed Income, Net Deductions	$ 0	$ 1,573	$ 0
Effective Income Tax Rate Reconciliation, Tax Credit, Percent	0.00%	(4.20%)	0.00%
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount	$ 30	$ (10)	$ 1,578
Effective Income Tax Rate Reconciliation, Repatriation of Foreign Earnings, Amount	$ 0	$ 118	$ 1,767
Other, net, effective tax rate	4.40%	1.40%	1.20%
Effective Income Tax Rate Reconciliation, Tax Contingency, Amount	$ (1)	$ 19	$ (3)