Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2014

Stock-Based Compensation [Abstract]

Weighted average assumptions used to determine fair value for stock awards

The fair value for stock awards was estimated at the date of grant using the Black-Scholes option valuation model with the following weighted average assumptions for the years ended December 31, 2014, 2013 and 2012:

	2014			2013			2012
Expected life (in years)		6.5			6.9			6.9
Interest rate		2.16	%		1.22	%		1.36	%
Volatility		37.15	%		37.82	%		31.26	%
Expected dividend yield		0.34	%		0.48	%		0.31	%

Summary of stock option activity

The following table summarizes stock option activity for the year ended December 31, 2014:

	Awards			Weighted Average Exercise Price Per Share		Weighted Average Remaining Contractual Life (Years)		Aggregate Intrinsic Value (Millions)
Awards outstanding at December 31, 2013		1,131,415		$	32.42
Granted		173,068			58.25
Exercised		(323,636	)		30.57
Canceled		(29,768	)		41.88
Awards outstanding at December 31, 2014		951,079			37.46		6.67		30.4
Awards exercisable at December 31, 2014		631,487			31.55		5.75		23.9

Non-vested stock option activity

Non-vested stock option activity for the year ended December 31, 2014 is as follows:

	Awards			Weighted Average Grant date Fair Value Per Share
Nonvested awards outstanding at December 31, 2013		373,401		$	38.01
Granted		173,068			58.25
Vested		(197,109	)		37.17
Canceled		(29,768	)		41.88
Nonvested awards outstanding at December 31, 2014		319,592			49.13

Summary of restricted stock activity

The following table summarizes the restricted stock activity for the Plan:

	Awards			Weighted Average Grant Date Fair Value Per Share
Unvested balance at December 31, 2013		185,572		$	37.65
Granted		106,116			58.94
Vested		(61,621	)		36.51
Canceled		(55,038	)		38.73
Unvested balance at December 31, 2014		175,029			50.56