Stockholders' equity (Tables)

3 Months Ended

Mar. 31, 2018

Stockholders' equity

Summary of stock option activity

The following table summarizes stock option activity for the three months ended March 31, 2018 (shares and intrinsic value in thousands):

	Number of shares	Weighted-average exercise price		Weighted-average remaining contractual term	Aggregate intrinsic value
Outstanding at December 31, 2017	2,898	$	11.62	6.5	$	1,738
Granted	10	11.70		6.0	—
Exercised	—	—		—	—
Forfeited	—	—		—	—
Expired	—	—		—	—
Outstanding at March 31, 2018	2,908	$	11.62	6.3	$	1,339
Vested at March 31, 2018	1,937	$	11.73	5.6	$	1,024
Exercisable at March 31, 2018	1,937	$	11.73	5.6	$	1,024

Summary of restricted share activity

The following table summarizes restricted share activity for the three months ended March 31, 2018 (shares in thousands):

	Number of shares	Weighted-average grant date fair value
Outstanding at December 31, 2017	504	$	10.23
Granted	—	—
Vested	—	—
Forfeited	—	—
Outstanding at March 31, 2018	504	$	10.23

Time Based Stock Option | Black Scholes Pricing Model

Stockholders' equity

Schedule of valuation assumptions

Black-Scholes Option Valuation Assumptions	Three Months Ended March 31, 2018		Year Ended December 31, 2017
Risk-free interest rate	2.65	%	2.18	%
Dividend yield	—		—
Volatility	39.0	%	25.8	%
Weighted-average expected term (years)	6.0		6.0