Stockholders' Equity (Summary of Options by Range of Exercise Prices) (Details) shares in Thousands	9 Months Ended
	Sep. 30, 2017 $ / 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	7,704
Options outstanding, Weighted-average remaining contractual life	6 years 1 month 21 days
Options outstanding, Weighted-average exercise price (in dollars per share)	$ 10.47
Options exercisable, Number of shares (in shares) | shares	5,151
Options exercisable, Weighted-average exercise price (in dollars per share)	$ 11.18
$1.79 - $7.02
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, minimum (in dollars per share)	1.79
Exercise price range, maximum (in dollars per share)	$ 6.80
Options outstanding, Number of shares outstanding (in shares) | shares	892
Options outstanding, Weighted-average remaining contractual life	3 years 9 months 15 days
Options outstanding, Weighted-average exercise price (in dollars per share)	$ 5.23
Options exercisable, Number of shares (in shares) | shares	674
Options exercisable, Weighted-average exercise price (in dollars per share)	$ 4.81
$7.04 - $7.45
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, minimum (in dollars per share)	6.97
Exercise price range, maximum (in dollars per share)	$ 8.48
Options outstanding, Number of shares outstanding (in shares) | shares	356
Options outstanding, Weighted-average remaining contractual life	7 years 9 months 22 days
Options outstanding, Weighted-average exercise price (in dollars per share)	$ 7.26
Options exercisable, Number of shares (in shares) | shares	227
Options exercisable, Weighted-average exercise price (in dollars per share)	$ 7.22
$7.60 - $7.60
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, minimum (in dollars per share)	8.50
Exercise price range, maximum (in dollars per share)	$ 9.34
Options outstanding, Number of shares outstanding (in shares) | shares	875
Options outstanding, Weighted-average remaining contractual life	9 years 7 months 2 days
Options outstanding, Weighted-average exercise price (in dollars per share)	$ 7.60
Options exercisable, Number of shares (in shares) | shares	0
Options exercisable, Weighted-average exercise price (in dollars per share)	$ 0.00
$7.95 - $9.24
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, minimum (in dollars per share)	9.44
Exercise price range, maximum (in dollars per share)	$ 10.05
Options outstanding, Number of shares outstanding (in shares) | shares	775
Options outstanding, Weighted-average remaining contractual life	6 years 3 months 10 days
Options outstanding, Weighted-average exercise price (in dollars per share)	$ 8.97
Options exercisable, Number of shares (in shares) | shares	601
Options exercisable, Weighted-average exercise price (in dollars per share)	$ 9.16
$9.34 - $10.05
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, minimum (in dollars per share)	10.13
Exercise price range, maximum (in dollars per share)	$ 10.13
Options outstanding, Number of shares outstanding (in shares) | shares	853
Options outstanding, Weighted-average remaining contractual life	7 years 6 months 11 days
Options outstanding, Weighted-average exercise price (in dollars per share)	$ 9.75
Options exercisable, Number of shares (in shares) | shares	502
Options exercisable, Weighted-average exercise price (in dollars per share)	$ 9.82
$10.13 - $10.31
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, minimum (in dollars per share)	10.31
Exercise price range, maximum (in dollars per share)	$ 12.32
Options outstanding, Number of shares outstanding (in shares) | shares	781
Options outstanding, Weighted-average remaining contractual life	6 years 1 month 13 days
Options outstanding, Weighted-average exercise price (in dollars per share)	$ 10.14
Options exercisable, Number of shares (in shares) | shares	585
Options exercisable, Weighted-average exercise price (in dollars per share)	$ 10.13
$10.53 - $11.96
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)	$ 13.28
Options outstanding, Number of shares outstanding (in shares) | shares	795
Options outstanding, Weighted-average remaining contractual life	6 years 8 months 5 days
Options outstanding, Weighted-average exercise price (in dollars per share)	$ 11.03
Options exercisable, Number of shares (in shares) | shares	394
Options exercisable, Weighted-average exercise price (in dollars per share)	$ 11.17
$12.09 - $13.28
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, minimum (in dollars per share)	13.34
Exercise price range, maximum (in dollars per share)	$ 16.98
Options outstanding, Number of shares outstanding (in shares) | shares	1,041
Options outstanding, Weighted-average remaining contractual life	4 years 2 months 12 days
Options outstanding, Weighted-average exercise price (in dollars per share)	$ 13.05
Options exercisable, Number of shares (in shares) | shares	997
Options exercisable, Weighted-average exercise price (in dollars per share)	$ 13.04
$13.34 - $16.98
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, minimum (in dollars per share)	17.88
Exercise price range, maximum (in dollars per share)	$ 18.09
Options outstanding, Number of shares outstanding (in shares) | shares	1,042
Options outstanding, Weighted-average remaining contractual life	5 years 6 months
Options outstanding, Weighted-average exercise price (in dollars per share)	$ 15.24
Options exercisable, Number of shares (in shares) | shares	877
Options exercisable, Weighted-average exercise price (in dollars per share)	$ 15.56
$17.88 - $18.24
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, minimum (in dollars per share)	18.24
Exercise price range, maximum (in dollars per share)	$ 18.24
Options outstanding, Number of shares outstanding (in shares) | shares	294
Options outstanding, Weighted-average remaining contractual life	4 years 3 months 29 days
Options outstanding, Weighted-average exercise price (in dollars per share)	$ 18.06
Options exercisable, Number of shares (in shares) | shares	294
Options exercisable, Weighted-average exercise price (in dollars per share)	$ 18.06