Stockholders' Equity (Summary of Options by Range of Exercise Prices) (Details) shares in Thousands	3 Months Ended
	Mar. 31, 2019 $ / shares shares
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options outstanding, Number of shares outstanding (in shares) | shares	5,757
Options outstanding, Weighted-average remaining contractual life	6 years 10 months 28 days
Options outstanding, Weighted-average exercise price (in dollars per share)	$ 12.81
Options exercisable, Number of shares (in shares) | shares	3,093
Options exercisable, Weighted-average exercise price (in dollars per share)	$ 11.38
$3.35 - $7.60
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, minimum (in dollars per share)	3.35
Exercise price range, maximum (in dollars per share)	$ 7.60
Options outstanding, Number of shares outstanding (in shares) | shares	903
Options outstanding, Weighted-average remaining contractual life	6 years 5 months 19 days
Options outstanding, Weighted-average exercise price (in dollars per share)	$ 7.30
Options exercisable, Number of shares (in shares) | shares	475
Options exercisable, Weighted-average exercise price (in dollars per share)	$ 7.15
$7.95 - $10.01
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, minimum (in dollars per share)	7.95
Exercise price range, maximum (in dollars per share)	$ 10.01
Options outstanding, Number of shares outstanding (in shares) | shares	655
Options outstanding, Weighted-average remaining contractual life	6 years 4 months 6 days
Options outstanding, Weighted-average exercise price (in dollars per share)	$ 9.33
Options exercisable, Number of shares (in shares) | shares	535
Options exercisable, Weighted-average exercise price (in dollars per share)	$ 9.35
$10.05 - $10.60
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, minimum (in dollars per share)	10.05
Exercise price range, maximum (in dollars per share)	$ 10.60
Options outstanding, Number of shares outstanding (in shares) | shares	664
Options outstanding, Weighted-average remaining contractual life	5 years 8 months 19 days
Options outstanding, Weighted-average exercise price (in dollars per share)	$ 10.26
Options exercisable, Number of shares (in shares) | shares	658
Options exercisable, Weighted-average exercise price (in dollars per share)	$ 10.26
$11.33 - $12.32
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, minimum (in dollars per share)	11.33
Exercise price range, maximum (in dollars per share)	$ 12.32
Options outstanding, Number of shares outstanding (in shares) | shares	360
Options outstanding, Weighted-average remaining contractual life	7 years 22 days
Options outstanding, Weighted-average exercise price (in dollars per share)	$ 11.81
Options exercisable, Number of shares (in shares) | shares	176
Options exercisable, Weighted-average exercise price (in dollars per share)	$ 11.77
$12.45 - $12.45
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, minimum (in dollars per share)	12.45
Exercise price range, maximum (in dollars per share)	$ 12.45
Options outstanding, Number of shares outstanding (in shares) | shares	855
Options outstanding, Weighted-average remaining contractual life	2 years 10 months 6 days
Options outstanding, Weighted-average exercise price (in dollars per share)	$ 12.45
Options exercisable, Number of shares (in shares) | shares	158
Options exercisable, Weighted-average exercise price (in dollars per share)	$ 12.45
$12.46 - $13.59
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, minimum (in dollars per share)	12.46
Exercise price range, maximum (in dollars per share)	$ 13.59
Options outstanding, Number of shares outstanding (in shares) | shares	643
Options outstanding, Weighted-average remaining contractual life	9 years 4 months 17 days
Options outstanding, Weighted-average exercise price (in dollars per share)	$ 13.30
Options exercisable, Number of shares (in shares) | shares	643
Options exercisable, Weighted-average exercise price (in dollars per share)	$ 13.30
$14.30 - $16.05
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, minimum (in dollars per share)	14.30
Exercise price range, maximum (in dollars per share)	$ 16.05
Options outstanding, Number of shares outstanding (in shares) | shares	580
Options outstanding, Weighted-average remaining contractual life	3 years 9 months 4 days
Options outstanding, Weighted-average exercise price (in dollars per share)	$ 14.84
Options exercisable, Number of shares (in shares) | shares	149
Options exercisable, Weighted-average exercise price (in dollars per share)	$ 15.08
$16.35 - $21.05
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, minimum (in dollars per share)	16.35
Exercise price range, maximum (in dollars per share)	$ 21.05
Options outstanding, Number of shares outstanding (in shares) | shares	621
Options outstanding, Weighted-average remaining contractual life	8 years 8 months 19 days
Options outstanding, Weighted-average exercise price (in dollars per share)	$ 17.76
Options exercisable, Number of shares (in shares) | shares	299
Options exercisable, Weighted-average exercise price (in dollars per share)	$ 17.46
$21.10 - $25.36
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, minimum (in dollars per share)	21.10
Exercise price range, maximum (in dollars per share)	$ 25.36
Options outstanding, Number of shares outstanding (in shares) | shares	360
Options outstanding, Weighted-average remaining contractual life	6 years 11 months 1 day
Options outstanding, Weighted-average exercise price (in dollars per share)	$ 22.67
Options exercisable, Number of shares (in shares) | shares	0
Options exercisable, Weighted-average exercise price (in dollars per share)	$ 0.00
$25.95 - $25.95
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, minimum (in dollars per share)	25.95
Exercise price range, maximum (in dollars per share)	$ 25.95
Options outstanding, Number of shares outstanding (in shares) | shares	116
Options outstanding, Weighted-average remaining contractual life	9 years 9 months 26 days
Options outstanding, Weighted-average exercise price (in dollars per share)	$ 25.95
Options exercisable, Number of shares (in shares) | shares	0
Options exercisable, Weighted-average exercise price (in dollars per share)	$ 0.00