Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2016

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, 2016, 2015 and 2014:

	2016			2015			2014
Expected life (in years)		6.5			6.4			6.5
Interest rate		1.72	%		1.52	%		2.16	%
Volatility		36.75	%		36.86	%		37.15	%
Expected dividend yield		0.54	%		0.33	%		0.34	%

Summary of stock option activity

The following table summarizes stock option activity for the year ended December 31, 2016:

	Awards			Weighted Average Exercise Price Per Share		Weighted Average Remaining Contractual Life (Years)		Aggregate Intrinsic Value (Millions)
Awards outstanding at December 31, 2015		1,091,844		$	42.29
Granted		383,622			38.59
Exercised		(150,944	)		36.66
Canceled		(125,797	)		43.78
Awards outstanding at December 31, 2016		1,198,725			41.66		6.51	$	42.7
Awards exercisable at December 31, 2016		767,313			39.43		5.31		29.0

Non-vested stock option activity

Non-vested stock option activity for the year ended December 31, 2016 is as follows:

	Awards			Weighted Average Grant date Fair Value Per Share
Nonvested awards outstanding at December 31, 2015		353,859		$	57.21
Granted		383,622			38.59
Vested		(191,775	)		55.01
Canceled		(114,294	)		42.18
Nonvested awards outstanding at December 31, 2016		431,412			45.61

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, 2015		284,245			58.63
Granted		155,165			38.37
Vested		(88,746	)		57.38
Canceled		(123,451	)		50.72
Unvested balance at December 31, 2016		227,213			49.57