Stockholders' equity (Tables)

6 Months Ended

Jun. 30, 2019

Stockholders' equity

Summary of stock option activity

The following table summarizes stock option activity for the six months ended June 30, 2019 (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, 2018	2,910	$	11.62	5.6	$	2,806
Granted	—		—	—		—
Exercised	(9)		11.63	—		—
Forfeited	—		—	—		—
Expired	—		—	—		—
Outstanding at June 30, 2019	2,901	$	11.62	5.1	$	4,649
Vested at June 30, 2019	2,464	$	11.73	5.1	$	3,725
Exercisable at June 30, 2019	2,464	$	11.73	5.1	$	3,725

Summary of restricted share activity

The following table summarizes restricted share activity for the six months ended June 30, 2019 (shares in thousands):

		Weighted-average
	Number of shares	grant date fair value
Outstanding at December 31, 2018	370	$	9.86
Granted	76		14.46
Vested	(184)		11.88
Forfeited	—		—
Outstanding at June 30, 2019	262	$	9.76

Time Based Stock Option | Black Scholes Pricing Model

Stockholders' equity

Schedule of valuation assumptions

	Six Months Ended	Year Ended
Black-Scholes Option Valuation Assumptions	June 30, 2019	December 31, 2018
Risk-free interest rate	—	2.7% - 3.0	%
Dividend yield	—	—
Volatility	—	39.0% - 41.0	%
Weighted-average expected term (years)	—	6.0