Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2018

Equity [Abstract]

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,
	2018		2017		2016
Restricted Stock Awards	$	3,483	$	4,263	$	2,975
Restricted Stock Units	$	835	$	502	$	1,255
Stock Option Awards	$	1,878	$	2,439	$	2,352

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, 2017	543		$	16.23
Granted	309		$	17.45
Vested	(184	)	$	17.62
Forfeited	(41	)	$	17.39
Unvested balance at December 31, 2018	627		$	17.14

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 2018, 2017, and 2016 are presented below.

	2018	2017	2016
Expected life from date of grant (years)	5.3	5.3	4.4
Expected volatility	36.2%	42.0%	39.8%
Expected dividend yield	—%	—%	—%
Risk-free interest rate	2.50%	1.97%	1.16%

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, 2017	1,979	$	19.52	5.5	$	1,431
Issued	252	17.34
Outstanding balance at December 31, 2018	2,231	$	19.27	4.8	$	—
Exercisable, end of year	1,440	$	19.66	3.8	$	—