Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2016

Dec. 31, 2014

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Schedule of Share-based Compensation, Stock Options, Activity [Table Text Block]

Stock option activity in 2016 and 2015 are summarized in the following table:

	Outstanding		Weighted Average Exercise Price		Remaining Contractual Life in Years	Aggregate Intrinsic Value
Balance at December 31, 2014	1,819,444		$	20.28
Granted	—		$	—
Exercised	(420,642	)	$	17.29
Canceled	(117,269	)	$	21.80
Expired	(905,500	)	$	22.05
Balance at December 31, 2015	376,033		$	18.89	3.6	$	452,128
Granted	—		—
Exercised	(86,908	)	$	18.77
Canceled	(24,750	)	$	21.51
Expired	(32,750	)	$	17.56
Balance at December 31, 2016	231,625		$	18.88
Options vested or expected to vest at December 31, 2016	231,625		$	18.88	3.1	$	1,845,263
Exercisable at December 31, 2016	231,625		$	18.88	3.1	$	1,845,263

Schedule of Share-based Compensation, Shares Authorized under Stock Option Plans, by Exercise Price Range [Table Text Block]

Stock options outstanding at December 31, 2016 and 2015 are summarized in the following tables:

Range of Exercise Prices					Options Outstanding at 12/31/2016	Weighted Average Remaining Contractual Life (in Years)	Weighted Average Exercise Price		Options Exercisable at 12/31/2016	Weighted Average Exercise Price
$	15.17	—	$	16.54	54,625	3.0	$	15.68	54,625	$	15.68
$	16.55	—	$	17.58	36,000	5.5	$	16.95	36,000	$	16.95
$	17.59	—	$	20.20	54,000	2.3	$	18.16	54,000	$	18.16
$	20.21	—	$	22.21	51,000	1.4	$	21.84	51,000	$	21.84
$	22.22	—	$	22.57	36,000	4.4	$	22.57	36,000	$	22.57
					231,625	3.1	$	18.88	231,625	$	18.88

Range of Exercise Prices					Options Outstanding at 12/31/2015	Weighted Average Remaining Contractual Life (in Years)	Weighted Average Exercise Price		Options Exercisable at 12/31/2015	Weighted Average Exercise Price
$	15.17	—	$	16.54	84,250	4.0	$	15.74	84,250	$	15.74
$	16.55	—	$	17.63	89,833	3.6	$	17.23	89,833	$	17.23
$	17.64	—	$	20.20	61,500	3.1	$	18.21	61,500	$	18.21
$	20.21	—	$	22.17	79,250	2.4	$	21.84	79,250	$	21.84
$	22.18	—	$	22.57	61,200	5.4	$	22.55	61,200	$	22.55
					376,033	3.6	$	18.89	376,033	$	18.89

Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity [Table Text Block]

Restricted stock activity in 2016 and 2015 are summarized in the following table:

	Number of Awards		Weighted Average Grant Date Fair Value		Weighted Average Remaining Amortization Period (in Years)
Balance at December 31, 2014	252,476		$	18.93
Granted	23,814		$	18.31
Vested	(65,293	)	$	18.61
Canceled	(18,704	)	$	18.56
Balance at December 31, 2015	192,293		$	19.20	1.7
Granted	—		$	—
Vested	(42,546	)	$	18.47
Canceled	(5,452	)	$	18.75
Balance at December 31, 2016	144,295		$	19.43	0.5

Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table Text Block]

Stock-based compensation expense related to our equity incentive plans in accordance with U.S. GAAP was allocated as follows:

Year Ended December 31,	2016			2015			2014
(Thousands of dollars)
Cost of sales	$	472		$	370		$	113
Selling, general and administrative expenses	3,218			2,437			2,202
Stock-based compensation expense before income taxes	3,690			2,807			2,315
Income tax benefit	(1,361		)	(1,044		)	(740		)
Total stock-based compensation expense after income taxes	$	2,329		$	1,763		$	1,575

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]