Equity Incentive Plans (Tables)

12 Months Ended

Dec. 31, 2014

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

Summary of Stock Option and Restricted Stock Bonus Activities

The following summarizes stock option and restricted stock bonus activities for the years ended December 31, 2014, 2013 and 2012 after giving effect to the corporate conversion. At the date of grant, all options had an exercise price above the fair value of common stock:

	Number of Options			Weighted Average Exercise Price of Stock Options		Aggregate Intrinsic Value of Stock Options		Weighted Average Remaining Contractual Life of Stock Options
Outstanding at January 1, 2012		2,008,960		$	6.79		2,773		8.1 years
Granted		1,319,500			8.29		—		—
Forfeited		(95,271	)		11.07		—		—
Exercised		(155,708	)		5.88		—		—
Outstanding at December 31, 2012		3,077,481		$	7.35		26,385		7.9 years
Vested and expected to vest at December 31, 2012		3,021,937			7.32		25,988		7.9 years
Exercisable at December 31, 2012		1,726,891			6.54		16,203		7.0 years
Outstanding at January 1, 2013		3,077,481			7.35		26,385		7.9 years
Granted		455,000			17.08		—		—
Forfeited		(8,360	)		10.89		—		—
Exercised		(579,476	)		7.44		—		—
Outstanding at December 31, 2013		2,944,645		$	8.82		31,558		7.3 years
Vested and expected to vest at December 31, 2013		2,916,184			8.78		31,376		7.3 years
Exercisable at December 31, 2013		1,946,475			7.00		24,325		6.7 years
Outstanding at January 1, 2014		2,944,645		$	8.82		31,558		7.3 years
Granted		310,000			16.75		—		—
Forfeited		(31,905	)		8.34		—		—
Exercised		(6,795	)		7.03		—		—
Outstanding at December 31, 2014		3,215,945		$	9.60		39,615		6.6 years
Vested and expected to vest at December 31, 2014		3,204,967			9.58		39,610		6.6 years
Exercisable at December 31, 2014		2,760,402			8.70		39,187		6.3 years

Assumptions used in Black-Scholes Option-Pricing Model on Weighted Average Basis

The following summarizes the grant-date fair value of options granted for the years ended December 31, 2014, 2013 and 2012 and assumptions used in the Black-Scholes option-pricing model on a weighted average basis:

	Year Ended December 31,
	2014			2013			2012
Grant-date fair value of option	$	4.10		$	4.30		$	2.70
Expected term		2.7 Years			2.8 Years			3.0 Years
Risk-free interest rate		0.7	%		0.4	%		0.4	%
Expected volatility		36.7	%		37.6	%		48.8	%
Expected dividends		—			—			—

Number and Weighted Average Grant-Date Fair Value of Unvested Stock Options

The number and weighted average grant-date fair value of the unvested stock options are as follows:

	Year Ended December 31,
	2014					2013					2012
	Number			Weighted Average Grant- Date Fair Value		Number			Weighted Average Grant- Date Fair Value		Number			Weighted Average Grant- Date Fair Value
Unvested options at the beginning of the period		998,170		$	3.69		1,350,590		$	2.79		796,514		$	2.60
Granted options during the period		310,000			4.10		455,000			4.30		1,319,500			2.70
Vested options during the period		(819,818	)		3.61		(651,530	)		2.68		(654,022	)		2.32
Forfeited options during the period		(31,905	)		3.20		(7,106	)		3.92		(74,335	)		4.02
Exercised options during the period		(904	)		3.16		(148,784	)		2.46		(37,067	)		1.87
Unvested options at the end of the period		455,543		$	4.18		998,170		$	3.69		1,350,590		$	2.79