Share-Based Compensation (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Share-based Compensation [Abstract]
Shares available for future grants	12,000,000		12,000,000
Weighted-Average Price [Abstract]
Share-based compensation	$ 7.1	$ 6.6	$ 13.2	$ 12.3
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		1,809,019
Options Excercisable (in shares)	1,231,704		1,231,704
Unvested Options (in shares)	577,315		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		$ 27.90
Weighted-Average Price, Options Excercisable	$ 26.35		$ 26.35
Weighted-Average Price, Unvested Options	$ 31.22		$ 31.22
Weighted-Average Remaining Contractual Term, Outstanding			4 years 2 months 12 days
Aggregate Intrinsic Value, Outstanding	3.7		3.7
Weighted-Average Remaining Contractual Term, Options Excercisable			3 years 3 months 17 days
Aggregate Intrinsic Value, Options Excercisable	3.7		3.7
Weighted-Average Remaining Contractual Term, Unvested Options			6 years 1 month 5 days
Aggregate Intrinsic Value, Unvested Options	0		0
Intrinsic value of options exercised			4.2	6.9
Unrecognized compensation cost	5.5		5.5
Weighted-average period for recognition of compensation costs			2 years 4 months 24 days
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			15.0	12.6
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense			(0.3)	(0.1)
Restricted Shares Outstanding [Roll Forward]
Balance, beginning (in shares)			1,300,588
Granted (in shares)			810,248
Vested (in shares)			(499,193)
Forfeited (in shares)			(42,739)
Balance, Ending (in shares)	1,568,904		1,568,904
Weighted-Average Price [Abstract]
Weighted-Average Price, beginning balance (in dollars per share)			$ 31.78
Weighted-Average Price, Granted (in dollars per share)			$ 30.10	$ 30.74
Weighted-Average Price, Vested (in dollars per share)			$ 31.73
Weighted-Average Price, Forfeited (in dollars per share)			$ 31.07
Weighted-Average Price, Ending Balance (in dollars per share)	$ 30.94		$ 30.94
Unrecognized compensation cost	28.8		28.8
Weighted-average period for recognition of compensation costs			2 years 4 months 24 days
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)			(1,163)
Balance, Ending (in shares)	499,894		499,894
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)			$ (30.12)
Weighted-Average Price, Ending Balance (in dollars per share)	$ 32.33		$ 32.33
Unrecognized compensation cost	$ 9.7		$ 9.7
Weighted-average period for recognition of compensation costs			2 years 2 months 12 days