Stock-Based Compensation (Details 2) (Non-qualified stock options, USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 group Y	Dec. 31, 2010 Y	Dec. 31, 2009 Y	Dec. 31, 2008 Y
Summary of option activity
Vesting period (in years)	3 years
Expiration from date of grant (in years)	P10Y
Outstanding at the beginning of the period	4.5	4.1	3.4
Options granted	0.6	0.9	1.0
Options exercised	(1.6)	(0.4)	(0.1)
Options expired or forfeited	(0.1)	(0.1)	(0.2)
Outstanding at the end of the period	3.4	4.5	4.1
Weighted-Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)	$ 10.84	$ 10.67	$ 11.34
Options granted (in dollars per share)	$ 19.19	$ 10.92	$ 7.60
Options exercised (in dollars per share)	$ 8.17	$ 8.54	$ 5.78
Options expired or forfeited (in dollars per share)	$ 12.93	$ 14.68	$ 8.33
Outstanding at the end of the period (in dollars per share)	$ 13.55	$ 10.84	$ 10.67
Weighted-Average Remaining Contractual Life
Weighted-Average Remaining Contractual Life (in years)	6.45	5.16	5.06	4.82
Other disclosures
Aggregate intrinsic value of outstanding options	$ 38.0	$ 34.4
Aggregate intrinsic value of exercisable options	21.9	24.0
Total intrinsic value of options exercised	22.7	2.6
Total number of options exercisable (in shares)	2.1	2.9
Weighted average exercise price of options exercisable (in dollars per share)	$ 13.38	$ 11.15
Total unrecognized compensation cost on nonvested options	$ 2.1	$ 1.8
Information about outstanding non-qualified stock options
Exercise price, low end of range (in dollars per share)	$ 2.74
Exercise price, high end of range (in dollars per share)	$ 22.24
Number of Options Outstanding	3.4
Weighted Average Remaining Life (in Years)	6.45
Outstanding at the end of the period (in dollars per share)	$ 13.55
Number of Options Exercisable (in shares)	2.1
Outstanding at the end of the period (in dollars per share)	$ 13.38
Assumptions used in determining the estimated fair value of stock options
Risk-free interest rate (as a percent)	1.88%	2.40%	1.52%
Expected option life, Executive (in years)	4.84	5.51	4.97
Expected option life, Non-Executive (in years)	4.71	4.40	4.62
Dividend yield (as a percent)	0.00%
Volatility (as a percent)	44.08%	49.20%	61.75%
Weighted-average fair value per option granted	$ 7.65	$ 4.95	$ 3.96
Period of historical option activity considered to determine expected option life (in years)	10
Number of separate employee groups	2
Range of exercise prices $2.74 - $3.13
Information about outstanding non-qualified stock options
Exercise price, low end of range (in dollars per share)	$ 2.74
Exercise price, high end of range (in dollars per share)	$ 3.13
Number of Options Outstanding	0.1
Weighted Average Remaining Life (in Years)	1.07
Outstanding at the end of the period (in dollars per share)	$ 3.03
Number of Options Exercisable (in shares)	0.1
Outstanding at the end of the period (in dollars per share)	$ 3.03
Range of exercise prices $6.68 - $10.90
Information about outstanding non-qualified stock options
Exercise price, low end of range (in dollars per share)	$ 6.68
Exercise price, high end of range (in dollars per share)	$ 10.90
Number of Options Outstanding	1.7
Weighted Average Remaining Life (in Years)	6.78
Outstanding at the end of the period (in dollars per share)	$ 9.09
Number of Options Exercisable (in shares)	1.0
Outstanding at the end of the period (in dollars per share)	$ 8.47
Range of exercise prices $14.51 - $21.11
Information about outstanding non-qualified stock options
Exercise price, low end of range (in dollars per share)	$ 14.51
Exercise price, high end of range (in dollars per share)	$ 21.11
Number of Options Outstanding	1.4
Weighted Average Remaining Life (in Years)	6.60
Outstanding at the end of the period (in dollars per share)	$ 18.42
Number of Options Exercisable (in shares)	0.8
Outstanding at the end of the period (in dollars per share)	$ 17.82
Range of exercise prices $22.00 - $22.24
Information about outstanding non-qualified stock options
Exercise price, low end of range (in dollars per share)	$ 22.00
Exercise price, high end of range (in dollars per share)	$ 22.24
Number of Options Outstanding	0.2
Weighted Average Remaining Life (in Years)	4.19
Outstanding at the end of the period (in dollars per share)	$ 22.01
Number of Options Exercisable (in shares)	0.2
Outstanding at the end of the period (in dollars per share)	$ 22.01