Share-Based Compensation (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Share-based Compensation [Abstract]
Shares available for future grants	13,100,000		13,100,000
Total compensation expense related to share-based compensation	$ 7.2	$ 5.7	$ 19.5	$ 16.5
Stock Options [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Fair value of options at grant date			$ 14.29
Risk-free interest rate (in hundredths)			0.81%
Expected price volatility (in hundredths)			55.90%
Expected dividend yield (in hundredths)			0.26%
Expected life in years			5 years
Options Outstanding [RollForward]
Outstanding at December 31, 2011 (in shares)			2,003,694
Granted (in shares)			301,035
Exercised (in shares)			(336,675)
Forfeited (in shares)			0
Outstanding at June 30, 2012 (in shares)	1,968,054		1,968,054
Options Excercisable (in shares)	1,505,051		1,505,051
Unvested Options (in shares)	463,003		463,003
Weighted-Average Price [Abstract]
Weighted-Average Price, beginning (in dollars per share)			$ 21.23
Weighted-Average Price, Granted (in dollars per share)			$ 30.76
Weighted-Average Price, Exercised (in dollars per share)			$ 9.21
Weighted-Average Price, Forfeited (in dollars per share)			$ 0
Weighted-Average Price, Ending (in dollars per share)	$ 24.74		$ 24.74
Weighted-Average Price, Options Excercisable	$ 22.38		$ 22.38
Weighted-Average Price, Unvested Options	$ 32.43		$ 32.43
Weighted-Average Remaining Contractual Term, Outstanding			3 years 4 months 24 days
Aggregate Intrinsic Value, Outstanding	15.1		15.1
Weighted-Average Remaining Contractual Term, Options Excercisable			2 years 7 months 6 days
Aggregate Intrinsic Value, Options Excercisable	14.6		14.6
Weighted-Average Remaining Contractual Term, Unvested Options			5 years 10 months 24 days
Aggregate Intrinsic Value, Unvested Options	0.2		0.2
Intrinsic value of options exercised			7.1	2.7
Unrecognized compensation cost	3.6		3.6
Weighted-average period for recognition of compensation costs			2 years 2 months 12 days
Restricted Stock [Member]
Weighted-Average Price [Abstract]
Weighted-Average Price, beginning balance (in dollars per share)			$ 32.80
Weighted-Average Price, Granted (in dollars per share)			$ 30.59	$ 39.26
Weighted-Average Price, Vested (in dollars per share)			$ 31.88
Weighted-Average Price, Forfeited (in dollars per share)			$ 32.70
Weighted-Average Price, Ending Balance (in dollars per share)	$ 31.85		$ 31.85
Unrecognized compensation cost	21.1		21.1
Weighted-average period for recognition of compensation costs			2 years 2 months 12 days
Total fair value of stock that vested			16.6	11.5
Restricted Shares Outstanding [Roll Forward]
Balance, beginning (in shares)			1,099,752
Granted (in shares)			778,780
Vested (in shares)			(538,668)
Forfeited (in shares)			(61,502)
Balance, Ending (in shares)	1,278,362		1,278,362
Restricted Stock [Member] | Maximum [Member]
Weighted-Average Price [Abstract]
Vesting period (in years)			4 years
Restricted Stock [Member] | Minimum [Member]
Weighted-Average Price [Abstract]
Vesting period (in years)			3 years
Performance Share Units [Member]
Weighted-Average Price [Abstract]
Weighted-Average Price, beginning balance (in dollars per share)			$ 39.07
Weighted-Average Price, Granted (in dollars per share)			$ 30.90	$ 39.07
Weighted-Average Price, Vested (in dollars per share)			$ 0.00
Weighted-Average Price, Forfeited (in dollars per share)			$ (35.69)
Weighted-Average Price, Ending Balance (in dollars per share)	$ 34.03		$ 34.03
Unrecognized compensation cost	$ 6.2		$ 6.2
Weighted-average period for recognition of compensation costs			2 years 1 month 17 days
Restricted Shares Outstanding [Roll Forward]
Balance, beginning (in shares)			115,274
Granted (in shares)			179,304
Vested (in shares)			0
Forfeited (in shares)			(12,713)
Balance, Ending (in shares)	281,865		281,865