Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2016

For stock options granted during the three months ended March 31, 2016 and March 28, 2015 valued using the Black-Scholes option valuation model, we used the following assumptions:


	Three Months Ended
	March 31, 2016		March 28, 2015
Risk-free interest rate		1.1% - 1.21%		0.99% - 1.06%
Expected dividend yield		0%		0%
Expected option life		4 years		3 years
Expected volatility		46.7%		42.3%
Weighted-average expected volatility		46.7%		42.3%

Assumptions Used to Estimate The Fair Value of The Performance-based Stock Options and Restricted Stock Units

The assumptions used to estimate the fair value of the performance-based stock options and restricted stock units granted during the three months ended March 28, 2015 and valued under the Monte Carlo Simulation model were as follows:


	Three Months Ended
	March 31, 2016		March 28, 2015
Risk-free interest rate		—		0.95% - 1.48%
Expected dividend yield		—		0%
Expected option life		—		4 years
Expected volatility		—		44.5%
Weighted-average expected volatility		—		44.5%

Summary of Stock Option Activity

A summary of stock option activity and weighted-average exercise prices for the three months ended March 31, 2016 follows:


	Options			Weighted- Average Exercise Price		Weighted-Average Remaining Contractual Term (Years)		Aggregate Intrinsic Value as of March 31, 2016
Outstanding at January 1, 2016		1,178,585		$	48.14
Granted		168,740			33.04
Forfeited		(142,694	)		43.17
Exercised		(103,073	)		17.38
Unearned performance-based options		(23,328	)		59.97

Outstanding at March 31, 2016		1,078,230		$	49.09		5.3	$	315,056


Options exercisable at March 31, 2016		567,175		$	50.55		3.8	$	181,256

Summary of Restricted Stock Activity

The following table summarizes the restricted stock and restricted stock unit activity and weighted average grant-date fair values for the three months ended March 31, 2016:


				Weighted-Average
				Grant Date
	Shares			Fair Value
Non-vested at January 1, 2016		15,916		$	43.47
Granted		109,714			33.05
Forfeited		(2,787	)		33.05
Vested		(464	)		42.29
Unearned performance-based awards		(677	)		53.03

Non-vested at March 31, 2016		121,702		$	34.32