Share-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2018

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

Schedule of grant date fair value and related assumptions of Options granted

	Year Ended December 31,
	2018	2017	2016
Option valuation assumptions:
Expected dividend yield	—%	—%	—%
Expected volatility	50%	66%	56%
Risk-free interest rate	2.71%	1.80%	1.64%
Expected term (in years)	6.3	6.2	6.3

Schedule of Share-based Compensation, Stock Options, Activity

A summary of the changes in stock options outstanding during the year ended December 31, 2018, is as follows:

	Number of Options		Weighted Average Exercise Price		Weighted Average Remaining Contract Term (years)	Aggregate Intrinsic Value (in thousands)
Options outstanding as of December 31, 2017	1,644,212		$	8.81
Granted	48,400		$	24.46
Exercised	(74,722	)	$	10.36
Canceled or forfeited	(102,429	)	$	10.73
Options outstanding as of December 31, 2018	1,515,461		9.11		6.57	21,125
Exercisable as of December 31, 2018	1,102,594		$	8.15	6.17	$	16,369

Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value

The following is provided for stock options granted:

	Year Ended December 31,
	2018		2017		2016
Weighted average grant date fair value	$	12.63	$	5.31	$	5.77

Nonvested Restricted Stock Shares Activity

A summary of the changes in restricted stock shares outstanding during the year ended December 31, 2018 is as follows:

	Shares Outstanding		Grant Date Fair Value (per share)
Outstanding as of December 31, 2017	77,715		$	6.43
Granted	331,013		29.43
Vested	(112,286	)	13.77
Canceled or forfeited	(8,963	)	31.74
Outstanding as of December 31, 2018	287,479		$	29.26