Stock Option Plans (Tables)

12 Months Ended

Dec. 31, 2012

Stock Option Plans [Abstract]

Summary of stock-based compensation expense

The following table is a summary of the stock-based compensation expense recognized for the years ended December 31, 2012, 2011 and 2010:

(Thousands of dollars)	2012			2011			2010
Stock options	$	5,162		$	4,881		$	4,627
Performance shares		288			-			-
Restricted stock awards and units		2,216			429			-
Total stock-based compensation expense		7,666			5,310			4,627
Tax benefit		(2,836	)		(1,964	)		(1,712	)
Total compensation expense, net of tax	$	4,830		$	3,346		$	2,915

Stock option valuation assumptions

The fair value of each option grant during the years ended December 31, 2012, 2011 and 2010 was estimated on the date of grant using the Black-Scholes option-pricing model with the following assumptions:

	2012			2011			2010
Expected dividend yield		0.64% -1.02	%		0.60% -0.80	%		0.94% - 1.60	%
Expected stock price volatility		45.00% - 56.40	%		48.10% - 57.90	%		51.20% - 57.80	%
Risk free interest rate		0.27% - 0.82	%		0.28% - 2.39	%		0.53% - 2.96	%
Expected life of options	2 - 4 years			3 - 4 years			2 - 6 years
Weighted-average fair value per share at grant date	$	63.84		$	26.29		$	17.05

Summary of stock options activity

A summary of stock option activity under the plans during the year ended December 31, 2012, is presented below:

						Weighted-
				Weighted-		Average		Aggregate
				Average		Remaining		Intrinsic
				Exercise		Contractual		Value
Options	Shares			Price		Term		($000's)
Outstanding at January 1, 2012		1,504,311		$	42.26
Granted		236,800			50.58
Exercised		(71,026	)		27.46
Forfeited or expired		(44,758	)		48.04
Outstanding at December 31, 2012		1,625,327			43.96		7.3		25,474
Exercisable at December 31, 2012		921,461			38.37		6.4		19,430

Summarizes information about performance shares that remain outstanding

The following table summarizes information about the performance shares that remain outstanding as of December 31, 2012:

										Weighted
	Target Shares							Target Shares		Average
	Outstanding at		Target		Target			Outstanding		Grant Date
Period	Beginning		Shares		Shares			at End		Fair Value
Granted	of Year		Granted		Forfeited			of Year		per Share
2012		-		70,151		(2,996	)		67,155	$	59.55
Total		-		70,151		(2,996	)		67,155

Summary of combined changes of RSAs and RSUs

A summary of the combined changes of RSAs and RSUs for the year ended December 31, 2012, is presented below:

				Weighted-
				Average
	Number of			Grant Date
Awards	Awards			Fair Value
Unvested at January 1, 2012		57,300		$	57.40
Granted		74,705			62.36
Vested		(19,102	)		57.40
Forfeited		(2,996	)		79.64
Unvested at December 31, 2012		109,907		$	60.13