Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2015

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 2015 and 2014:

	Outstanding		Weighted Average Exercise Price		Remaining Contractual Life in Years	Aggregate Intrinsic Value
Balance at December 31, 2013	2,466,606		$	20.31
Granted	—		$	—
Exercised	(453,745	)	$	16.36
Canceled	(72,167	)	$	22.37
Expired	(121,250	)	$	34.18
Balance at December 31, 2014	1,819,444		$	20.28	1.9	$	2,101,753
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
Options vested or expected to vest at December 31, 2015	376,033		$	18.89	3.6	$	452,128
Exercisable at December 31, 2015	376,033		$	18.89	3.6	$	452,128

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

Stock options outstanding at December 31, 2015 and 2014:

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

Range of Exercise Prices					Options Outstanding at 12/31/2014	Weighted Average Remaining Contractual Life (in Years)	Weighted Average Exercise Price		Options Exercisable at 12/31/2014	Weighted Average Exercise Price
$	15.17	—	$	17.63	436,600	3.8	$	16.72	407,597	$	16.71
$	17.64	—	$	19.36	397,167	1.3	$	18.43	395,500	$	18.43
$	19.37	—	$	21.78	240,000	0.6	$	20.63	240,000	$	20.63
$	21.79	—	$	22.54	360,377	1.8	$	21.91	360,377	$	21.91
$	22.55	—	$	25.00	385,300	1.5	$	24.48	385,300	$	24.48
					1,819,444	1.9	$	20.28	1,788,774	$	20.34

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

Restricted stock activity in 2015 and 2014:

	Number of Awards		Weighted Average Grant Date Fair Value		Weighted Average Remaining Amortization Period (in Years)
Balance at December 31, 2013	124,163		$	17.70
Granted	225,205		$	19.35
Vested	(82,199	)	$	17.88
Canceled	(14,693	)	$	18.18
Balance at December 31, 2014	252,476		$	18.93	2.1
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

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,	2015			2014			2013
(Thousands of dollars)
Cost of sales	$	370		$	113		$	214
Selling, general and administrative expenses	2,437			2,202			2,471
Stock-based compensation expense before income taxes	2,807			2,315			2,685
Income tax benefit	(1,044		)	(740		)	(762		)
Total stock-based compensation expense after income taxes	$	1,763		$	1,575		$	1,923

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

The fair value of each option grant was estimated as of the date of grant using the Black-Scholes option-pricing model with the following assumptions:

Year Ended December 31,	2012
Expected dividend yield (a)	3.7%
Expected stock price volatility (b)	41.2%
Risk-free interest rate (c)	1.4%
Expected option lives (d)	6.9 years
Weighted average grant date fair value of options granted during the period	$5.10