Stock-Based Compensation Schedule of Share-based Compensation, Shares Authorized under Stock Option Plans, by Exercise Price Range (Details) - Employee Stock Option [Member] $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) $ / shares shares
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price lower range limit	$ 30.91
Exercise price upper range limit	$ 30.91
Outstanding options | shares	2,239,442
Outstanding options, weighted average remaining contractual life (in years)	5 years 29 days
Outstanding options, weighted average exercise price (in dollars per share)	$ 24.48
Exercisable options | shares	1,585,813
Exercisable options, weighted average exercise price (in dollars per share)	$ 24.20
Unrecognized Compensation Cost (in Milliions) | $	$ 9.1
Weighted Average Period Of Recognition For Unrecognized Compensation Costs	2 years 2 months 1 day
Range 1 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price lower range limit	$ 9.66
Exercise price upper range limit	$ 15.65
Outstanding options | shares	248,914
Outstanding options, weighted average remaining contractual life (in years)	2 years 5 months 9 days
Outstanding options, weighted average exercise price (in dollars per share)	$ 12.60
Exercisable options | shares	207,434
Exercisable options, weighted average exercise price (in dollars per share)	$ 12.31
Range 2 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price lower range limit	15.68
Exercise price upper range limit	$ 18.65
Outstanding options | shares	233,231
Outstanding options, weighted average remaining contractual life (in years)	6 years 3 months 7 days
Outstanding options, weighted average exercise price (in dollars per share)	$ 17.71
Exercisable options | shares	151,036
Exercisable options, weighted average exercise price (in dollars per share)	$ 17.86
Range 3 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price lower range limit	18.80
Exercise price upper range limit	$ 22.00
Outstanding options | shares	247,124
Outstanding options, weighted average remaining contractual life (in years)	4 years 3 months 22 days
Outstanding options, weighted average exercise price (in dollars per share)	$ 20.74
Exercisable options | shares	178,284
Exercisable options, weighted average exercise price (in dollars per share)	$ 20.64
Range 4 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price lower range limit	22.53
Exercise price upper range limit	$ 24.10
Outstanding options | shares	263,740
Outstanding options, weighted average remaining contractual life (in years)	5 years 5 months 19 days
Outstanding options, weighted average exercise price (in dollars per share)	$ 23.16
Exercisable options | shares	181,485
Exercisable options, weighted average exercise price (in dollars per share)	$ 23.17
Range 5 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price lower range limit	24.57
Exercise price upper range limit	$ 27.75
Outstanding options | shares	391,028
Outstanding options, weighted average remaining contractual life (in years)	5 years 11 months 12 days
Outstanding options, weighted average exercise price (in dollars per share)	$ 26.74
Exercisable options | shares	286,208
Exercisable options, weighted average exercise price (in dollars per share)	$ 26.75
Range 6 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price lower range limit	30.12
Exercise price upper range limit	$ 30.12
Outstanding options | shares	275,626
Outstanding options, weighted average remaining contractual life (in years)	5 years 6 months 26 days
Outstanding options, weighted average exercise price (in dollars per share)	$ 29.10
Exercisable options | shares	199,898
Exercisable options, weighted average exercise price (in dollars per share)	$ 29.17
Range 7 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Outstanding options | shares	194,860
Outstanding options, weighted average remaining contractual life (in years)	5 years 6 months 22 days
Outstanding options, weighted average exercise price (in dollars per share)	$ 30.12
Exercisable options | shares	119,128
Exercisable options, weighted average exercise price (in dollars per share)	$ 30.12
Range 8 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price lower range limit	31.24
Exercise price upper range limit	$ 31.24
Outstanding options | shares	158,751
Outstanding options, weighted average remaining contractual life (in years)	4 years 3 months 26 days
Outstanding options, weighted average exercise price (in dollars per share)	$ 30.91
Exercisable options | shares	111,900
Exercisable options, weighted average exercise price (in dollars per share)	$ 30.91
Range 9 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price lower range limit	31.91
Exercise price upper range limit	$ 31.91
Outstanding options | shares	211,168
Outstanding options, weighted average remaining contractual life (in years)	5 years 2 months 9 days
Outstanding options, weighted average exercise price (in dollars per share)	$ 31.24
Exercisable options | shares	135,440
Exercisable options, weighted average exercise price (in dollars per share)	$ 31.24
Range 10 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Outstanding options | shares	15,000
Outstanding options, weighted average remaining contractual life (in years)	5 years 5 months 16 days
Outstanding options, weighted average exercise price (in dollars per share)	$ 31.91
Exercisable options | shares	15,000
Exercisable options, weighted average exercise price (in dollars per share)	$ 31.91