Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2014

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

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions

The following is a summary of the assumptions used for the stock options granted during the three months ended March 31, 2014 and 2013, respectively, using the Black-Scholes pricing model:

	Three Months Ended   March 31,
	2014		2013
Expected life (years)	5.77		5.86
Risk-free interest rate	1.73	%	0.77	%
Expected volatility	63.80	%	65.66	%
Expected dividend yield	—		—

Schedule of Share-based Compensation, Stock Options, Activity

The following table summarizes stock option activity during the three months ended March 31, 2014: 

	Shares		Weighted Average Exercise Price		Weighted Avg. Remaining Contractual Term (In Years)	Aggregate Intrinsic Value
Options outstanding at January 1, 2014	3,153,234		$	9.72
Granted	31,200		26.02
Exercised	(279,067	)	6.11
Canceled	(1,608	)	5.11
Options outstanding at March 31, 2014	2,903,759		$	10.24	7.20	$	58,265,652
Options exercisable at March 31, 2014	1,521,217		$	6.99	5.92	$	35,468,856