The fair value for options granted at the time of issuance were estimated at the date of grant using a Black-Scholes options pricing model. Significant assumptions included in the option value model include the fair value of our common stock at the grant date, weighted average volatility, risk-free interest rate, dividend yield and the forfeiture rate. There were no stock options granted in any of the periods presented.


		Weighted-Average		Contractual Terms
	Options	Exercise Price		(in Years)
Outstanding at January 1, 2019	112,094	$	30.32	1.8
Exercised	(21,409)	30.69

Outstanding at June 30, 2019	90,685	$	30.23	1.4

Options generally include a time-based vesting schedule permitting the options to vest ratably over three years. At June 30, 2019 and December 31, 2018, all options were fully vested.

There was no stock-based compensation expense on stock options for the three and six month periods ended June 30, 2019 and 2018, respectively.


		Weighted-Average
		Remaining
	Restricted	Contractual Terms
	Stock	(in Years)
Outstanding at January 1, 2019	177,293	2.2
Granted	139,619
Forfeited	(5,121)
Vested	(4,444)
Outstanding at June 30, 2019	307,347	2.1
Restricted stock exercisable at June 30, 2019	—

At June 30, 2019, there was $6,999 of unrecognized compensation expense remaining related to our service-based restricted stock awards. The unrecognized compensation cost was expected to be recognized over a weighted-average period of 2.1 years or earlier upon an elimination of the restriction period as a result of a change in control event.

Stock-based compensation expense on restricted stock amounted to $692 and $454 for the three months ended June 30, 2019 and 2018, respectively, and $1,163 and $2,631 for the six months ended June 30, 2019 and 2018, respectively.


		Weighted-Average
	Warrants	Exercise Price
Outstanding at January 1, 2019	6,790	$	27.81
Forfeited or expired	(1,811)	—
Outstanding at June 30, 2019	4,979	$	27.88

For all periods presented, the warrants were issued at exercise prices ranging from $26.27 to $30.97 per share. The warrants generally have a ten-year term. At June 30, 2019, no warrants had been exercised. At inception, no fair value was assigned to the warrants.