Stock-based Compensation Expense (Tables)

12 Months Ended

Dec. 31, 2012

The following table summarizes information about the Company’s fixed-price stock options as of and for the year ended December 31, 2012:


	Shares			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (Years)		Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2011		2,171,172		$	30.82		7.1	$	46,846
Granted		263,200			66.12
Exercised		(949,170	)		22.28
Forfeited		(141,941	)		49.62

Outstanding at December 31, 2012		1,343,261		$	41.78		7.2	$	28,232

Exercisable at December 31, 2012		773,427		$	30.39		6.4	$	24,539

Weighted-Average Assumptions used to Estimate Fair Value of Each Option Granted

The fair value of each option granted 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 weighted-average assumptions:


	Year Ended December 31,
	2012			2011			2010
Dividend yield		1.59	%		1.53	%		1.66	%
Volatility		34.04	%		33.04	%		33.13	%
Average expected life (years)		6			6			6
Risk-free interest rate		2.05	%		3.67	%		3.92	%
Fair value of options granted	$	20.00		$	18.42		$	13.76

Activity in Performance Unit Awards

The following table summarizes activity in performance unit awards:


	Year Ended December 31,
	2012					2011					2010
	Shares			Weighted Average Grant Date Fair Value		Shares			Weighted Average Grant Date Fair Value		Shares			Weighted Average Grant Date Fair Value
Nonvested, beginning of period		370,150		$	49.23		184,196		$	41.88		7,500		$	38.41
Granted		367,600			53.57		190,700			56.14		198,700			41.94
Vested		(276,250	)		44.44		(2,946	)		38.41		(2,947	)		38.41
Forfeited		(97,400	)		54.10		(1,800	)		48.26		(19,057	)		41.64

Nonvested, end of period		364,100			55.94		370,150			49.23		184,196			41.88

Activity in Non-Performance Based Restricted Stock Awards

The following table summarizes activity in non-performance based restricted stock awards:


	Year Ended December 31,
	2012					2011					2010
	Shares			Weighted Average Grant Date Fair Value		Shares			Weighted Average Grant Date Fair Value		Shares			Weighted Average Grant Date Fair Value
Nonvested, beginning of period		228,265		$	41.35		333,416		$	34.38		535,625		$	35.10
Granted		47,473			60.58		63,600			58.43		92,750			40.98
Vested		(116,586	)		34.08		(159,751	)		35.94		(250,126	)		37.48
Forfeited		(16,347	)		37.80		(9,000	)		48.64		(44,833	)		39.43

Nonvested, end of period		142,805			51.01		228,265			41.35		333,416			34.38