Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2017

Schedule of Compensation Cost for Share-based Payment Arrangements, Allocation of Share-based Compensation Costs by Plan

The following table summarizes our compensation costs recognized in General and administrative expense (excluding depreciation) and Operating expense (excluding depreciation) under the Incentive Plan and Stock Purchase Plan (in thousands):



	Years Ended December 31,
	2017		2016		2015
Restricted Stock Awards	$	4,263	$	2,975	$	3,692
Restricted Stock Units	$	502	$	1,255	$	—
Stock Option Awards	$	2,439	$	2,352	$	1,477

Schedule Of Equity Incentive Plan Disclosures

The following table summarizes our restricted stock activity, including performance restricted stock units, (in thousands, except per share amounts):



	Shares		Weighted- Average Grant Date Fair Value
Unvested balance at December 31, 2016	436		$	17.83
Granted	323		$	15.25
Vested	(207	)	$	18.77
Forfeited	(9	)	$	16.44
Unvested balance at December 31, 2017	543		$	16.23

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

The weighted-average assumptions used to measure stock options granted during 2017, 2016, and 2015 are presented below.



	2017	2016	2015
Expected life from date of grant (years)	5.3	4.4	6.4
Expected volatility	42.0%	39.8%	35.0%
Expected dividend yield	—%	—%	—%
Risk-free interest rate	1.97%	1.16%	1.81%

Schedule of Share-based Compensation, Stock Options, Activity

The following table summarizes our stock option activity (in thousands, except per share amounts):



	Number of Options		Weighted-Average Exercise Price		Weighted-Average Remaining Contractual Term in Years	Aggregate Intrinsic Value
Outstanding balance at December 31, 2016	1,743		$	20.13	6.2	$	—
Issued	239		15.03
Exercised	—		—
Forfeited / canceled	(3	)	15.15
Outstanding balance at December 31, 2017	1,979		$	19.52	5.5	$	1,431
Exercisable, end of year	1,094		$	19.51	4.3	$	1,329