Stockholders' equity (Tables)

9 Months Ended

Sep. 30, 2018

Stockholders' equity

Summary of stock option activity

The following table summarizes stock option activity for the nine months ended September 30, 2018 (shares and intrinsic value in thousands):

				Weighted-average
		Weighted-average		remaining contractual	Aggregate intrinsic
	Number of shares	exercise price		term	value
Outstanding at December 31, 2017	2,898	$	11.62	6.5	$	1,738
Granted	49		11.42	6.0		—
Exercised	(67)		13.38	—		—
Forfeited	(24)		12.30	—		—
Expired	(6)		12.10	—		—
Outstanding at September 30, 2018	2,850	$	11.57	5.8	$	7,169
Vested at September 30, 2018	2,143	$	11.70	5.4	$	5,196
Exercisable at September 30, 2018	2,143	$	11.70	5.4	$	5,196

Summary of restricted share activity

The following table summarizes restricted share activity for the nine months ended September 30, 2018 (shares in thousands):

		Weighted-average
	Number of shares	grant date fair value
Outstanding at December 31, 2017	504	$	10.23
Granted	93		11.85
Vested	(199)		11.50
Forfeited	(9)		11.85
Outstanding at September 30, 2018	389	$	9.93

Time Based Stock Option | Black Scholes Pricing Model

Stockholders' equity

Schedule of valuation assumptions

	Nine Months Ended		Year Ended
Black-Scholes Option Valuation Assumptions	September 30, 2018		December 31, 2017
Risk-free interest rate	2.7%   -   2.8	%	2.2	%
Dividend yield	—		—
Volatility	39.0	%	25.8	%
Weighted-average expected term (years)	6.0		6.0