Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2015

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, 2015, 2014 and 2013:

	2015		2014		2013
Expected life (in years)		6.4		6.5		6.9
Interest rate		1.52%		2.16%		1.22%
Volatility		36.86%		37.15%		37.82%
Expected dividend yield		0.33%		0.34%		0.48%

Summary of stock option activity

The following table summarizes stock option activity for the year ended December 31, 2015:

	Awards			Weighted Average Exercise Price Per Share		Weighted Average Remaining Contractual Life (Years)		Aggregate Intrinsic Value (Millions)
Awards outstanding at December 31, 2014		951,079		$	37.46
Granted		238,773			60.40
Exercised		(74,839	)		33.12
Canceled		(23,169	)		60.22
Awards outstanding at December 31, 2015		1,091,844			42.29		6.46		9.1
Awards exercisable at December 31, 2015		737,985			35.13		5.46		8.9

Non-vested stock option activity

Non-vested stock option activity for the year ended December 31, 2015 is as follows:

	Awards			Weighted Average Grant date Fair Value Per Share
Nonvested awards outstanding at December 31, 2014		319,592		$	49.13
Granted		238,773			60.40
Vested		(181,337	)		46.88
Canceled		(23,169	)		60.22
Nonvested awards outstanding at December 31, 2015		353,859			57.21

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, 2014		175,029		$	50.56
Granted		216,502			60.32
Vested		(59,801	)		47.51
Canceled		(47,944	)		51.43
Unvested balance at December 31, 2015		283,786			58.63