Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of Valuation Assumptions

For stock options granted during the nine months ended September 30, 2018 and September 30, 2017 valued using the Black-Scholes option valuation model, we used the following assumptions:

	Nine Months Ended
	September 30, 2018		September 30, 2017
Risk-free interest rate	2.65	%	1.88% - 2.02%
Expected dividend yield	—	%	—	%
Expected term of option	4 years		5 years
Expected volatility	45.0	%	45.2	%
Weighted-average expected volatility	45.0	%	45.2	%

Schedule of Stock Option Activity and Weighted Average Exercise Prices

A summary of stock option activity and weighted-average exercise prices during the nine months ended September 30, 2018 follows:

	Options		Weighted- Average Exercise Price		Weighted-Average Remaining Contractual Term (Years)	Aggregate Intrinsic Value as of September 30, 2018
Outstanding at January 1, 2018	1,156,763		$	45.93
Granted	174,439		61.30
Forfeited or expired	(72,785	)	51.66
Exercised	(439,677	)	47.25
Unearned performance-based options	(17,160	)	59.97
Outstanding at September 30, 2018	801,580		$	47.61	4.6	$	13,419
Options exercisable at September 30, 2018	393,321		$	49.65	2.1	$	5,780

Schedule of Restricted Stock and Restricted Stock Units Activity and Weighted-Average Grant Date Fair Value

The following table summarizes the restricted stock and restricted stock unit activity and weighted average grant-date fair values for the nine months ended September 30, 2018:

	Shares		Weighted-Average Grant Date Fair Value
Non-vested at January 1, 2018	257,492		$	34.75
Granted	102,458		60.26
Forfeited	(20,578	)	38.07
Vested	(18,618	)	35.03
Unearned performance-based awards	(640	)	51.15
Non-vested at September 30, 2018	320,114		$	42.64