Stock-based Compensation - Summary Information about Stock Options Outstanding (Details) - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options outstanding, weighted average exercise price (in dollars per share)	$ 25.56	$ 24.21
$10.01-15.00
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price, lower range limit (in dollars per share)	10.01
Exercise price, upper range limit (in dollars per share)	$ 15.00
Options Outstanding	61
Options outstanding, weighted average remaining contractual life (in years)	9 months 15 days
Options outstanding, weighted average exercise price (in dollars per share)	$ 14.11
Options Exercisable	61
Options exercisable, weighted average exercise price (in dollars per share)	$ 14.11
15.01-20.00
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price, lower range limit (in dollars per share)	15.01
Exercise price, upper range limit (in dollars per share)	$ 20.00
Options Outstanding	49
Options outstanding, weighted average remaining contractual life (in years)	2 years 1 month 24 days
Options outstanding, weighted average exercise price (in dollars per share)	$ 19.92
Options Exercisable	49
Options exercisable, weighted average exercise price (in dollars per share)	$ 19.92
20.01-25.00
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price, lower range limit (in dollars per share)	20.01
Exercise price, upper range limit (in dollars per share)	$ 25.00
Options Outstanding	586
Options outstanding, weighted average remaining contractual life (in years)	8 years 1 month 21 days
Options outstanding, weighted average exercise price (in dollars per share)	$ 22.67
Options Exercisable	191
Options exercisable, weighted average exercise price (in dollars per share)	$ 22.73
25.01-30.00
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price, lower range limit (in dollars per share)	25.01
Exercise price, upper range limit (in dollars per share)	$ 30.00
Options Outstanding	780
Options outstanding, weighted average remaining contractual life (in years)	8 years 4 months 13 days
Options outstanding, weighted average exercise price (in dollars per share)	$ 27.50
Options Exercisable	244
Options exercisable, weighted average exercise price (in dollars per share)	$ 28.09
30.01-32.20
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price, lower range limit (in dollars per share)	30.01
Exercise price, upper range limit (in dollars per share)	$ 32.20
Options Outstanding	176
Options outstanding, weighted average remaining contractual life (in years)	7 years 22 days
Options outstanding, weighted average exercise price (in dollars per share)	$ 32.10
Options Exercisable	120
Options exercisable, weighted average exercise price (in dollars per share)	$ 32.06
10.01-32.20
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price, lower range limit (in dollars per share)	10.01
Exercise price, upper range limit (in dollars per share)	$ 32.20
Options Outstanding	1,652
Options outstanding, weighted average remaining contractual life (in years)	7 years 8 months 9 days
Options outstanding, weighted average exercise price (in dollars per share)	$ 25.56
Options Exercisable	665
Options exercisable, weighted average exercise price (in dollars per share)	$ 25.39