Stock-Based Compensation (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares Available for Grant	1,998,881
Shares of common stock reserved for issuance	3,487,290
Restricted Stock Units Nonvested and Expected to Vest
Total compensation cost not yet recognized	$ 47.7
Total compensation cost not yet recognized - period for recognition	2 years
Employee Share Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued under the Employee Share Purchase Plan	163,143
Stock Options [Member]
Options Outstanding and Exercisable:
Options outstanding, number	751,853	870,000
Options exercisable, number	232,828
Options outstanding, weighted average exercise price	$ 50.18	$ 35.81
Options exercisable, weighted average exercise price	$ 31.80
Options outstanding, aggregate intrinsic value	29.5
Options exercisable, aggregate intrinsic value	13.4
Options outstanding, weighted average remaining contractual term (in years)	5 years 1 month 6 days
Options exercisable, weighted average remaining contractual term (in years)	3 years 9 months 18 days
Restricted Stock Units [Member]
Restricted Stock Units Nonvested and Expected to Vest
Restricted stock units nonvested, number	745,060	871,000
Restricted stock units expected to vest, number	637,692
Restricted stock units nonvested, weighted average grant date per share fair value	$ 57.60	$ 41.69
Restricted stock units expected to vest, weighted average grant date per share fair value	$ 56.75
Restricted stock units nonvested, aggregate intrinsic value	65.8
Restricted stock units expected to vest, aggregate intrinsic value	$ 57.0
Restricted stock units nonvested, weighted average remaining term to vest (in years)	1 year 8 months 12 days
Restricted stock units expected to vest, weighted average remaining term to vest (in years)	1 year 7 months 6 days
Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares Authorized	11,000,000	10,750,000
Employee Share Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares Authorized	3,950,000	3,700,000
Discount from market price under the Employee Share Purchase Plan	15.00%
Maximum number of shares that can be purchased per employee in the Employee Share Purchase Plan	500
Employee share purchase plan, weighted average purchase price per share	$ 52.60
Employee share purchase plan, weighted average discount per share	$ 27.36
Employee stock purchase plan, remaining number of shares authorized to be purchased	911,568