Share-Based Compensation (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Share-based Compensation [Abstract]
Shares available for future grants	12,000,000
Weighted-Average Price [Abstract]
Share-based compensation	$ 6.1	$ 5.7
Stock Options [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Fair value of options at grant date	$ 15.32
Risk-free interest rate (in hundredths)	0.97%
Expected price volatility (in hundredths)	58.50%
Expected dividend yield (in hundredths)	0.27%
Expected life in years	5 years 6 months
Options Outstanding [RollForward]
Outstanding Beginning Balance (in shares)	1,697,471
Granted (in shares)	321,048
Exercised (in shares)	(209,500)
Forfeited (in shares)	0
Outstanding Ending Balance (in shares)	1,809,019
Options Excercisable (in shares)	1,231,704
Unvested Options (in shares)	577,315
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense	1.4	2.1
Adjustment to Additional Paid in Capital, Income Tax Effect from Share-based Compensation, Net	1.4
Weighted-Average Price [Abstract]
Weighted-Average Price, beginning (in dollars per share)	$ 25.23
Weighted-Average Price, Granted (in dollars per share)	$ 30.12
Weighted-Average Price, Exercised (in dollars per share)	$ 9.60
Weighted-Average Price, Forfeited (in dollars per share)	$ 0
Weighted-Average Price, Ending (in dollars per share)	$ 27.90
Weighted-Average Price, Options Excercisable	$ 26.35
Weighted-Average Price, Unvested Options	$ 31.22
Weighted-Average Remaining Contractual Term, Outstanding	4 years 5 months
Aggregate Intrinsic Value, Outstanding	8.1
Weighted-Average Remaining Contractual Term, Options Excercisable	3 years 6 months
Aggregate Intrinsic Value, Options Excercisable	7.7
Weighted-Average Remaining Contractual Term, Unvested Options	6 years 5 months
Aggregate Intrinsic Value, Unvested Options	0.4
Intrinsic value of options exercised	4.2	6.9
Unrecognized compensation cost	6.6
Weighted-average period for recognition of compensation costs	2 years 7 months
Employee Service Share-based Compensation, Cash Received from Exercise of Stock Options	0.5
Restricted Stock [Member]
Options Outstanding [RollForward]
Total fair value of stock that vested	14.8	11.6
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense	(0.3)	(0.1)
Adjustment to Additional Paid in Capital, Income Tax Effect from Share-based Compensation, Net	(0.3)
Restricted Shares Outstanding [Roll Forward]
Balance, beginning (in shares)	1,300,588
Granted (in shares)	792,086
Vested (in shares)	(493,449)
Forfeited (in shares)	(22,014)
Balance, Ending (in shares)	1,577,211
Weighted-Average Price [Abstract]
Weighted-Average Price, beginning balance (in dollars per share)	$ 31.78
Weighted-Average Price, Granted (in dollars per share)	$ 30.12	$ 30.89
Weighted-Average Price, Vested (in dollars per share)	$ 31.74
Weighted-Average Price, Forfeited (in dollars per share)	$ 31.56
Weighted-Average Price, Ending Balance (in dollars per share)	$ 30.96
Unrecognized compensation cost	34.8
Weighted-average period for recognition of compensation costs	2 years 7 months
Restricted Stock [Member] | Minimum [Member]
Weighted-Average Price [Abstract]
Vesting period (in years)	3 years
Performance Share Units [Member]
Restricted Shares Outstanding [Roll Forward]
Balance, beginning (in shares)	283,484
Granted (in shares)	217,573
Vested (in shares)	0
Forfeited (in shares)	0
Balance, Ending (in shares)	501,057
Weighted-Average Price [Abstract]
Weighted-Average Price, beginning balance (in dollars per share)	$ 34.01
Weighted-Average Price, Granted (in dollars per share)	$ 30.12	$ 30.90
Weighted-Average Price, Vested (in dollars per share)	$ 0.00
Weighted-Average Price, Forfeited (in dollars per share)	$ 0.00
Weighted-Average Price, Ending Balance (in dollars per share)	$ 32.32
Unrecognized compensation cost	$ 11.1
Weighted-average period for recognition of compensation costs	2 years 5 months