Non-vested Award Activity (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Stock-based Compensation Nonvested Rollforward
Weighted-average years expected to be recognized over	1.4
Stock options
Stock-based Compensation Nonvested Rollforward
Total unrecognized compensation expense remaining	$ 7.1
Stock-settled awards
Stock-based Compensation Nonvested Rollforward
Non-vested as of January 1, 2011	15.0
Granted	0.8	3.7	7.8
Vested	(5.3)
Forfeited	(1.3)
Non-vested as of December 31, 2011	9.2	15.0
Nonvested as of January 1, 2011, Weighted-average grant date fair value	$ 6.96
Granted, Weighted-average grant-date fair value	$ 11.94	$ 8.47	$ 4.21
Vested, Weighted-average grant date fair value	$ 8.82
Forfeited, Weighted-average grant date fair value	$ 6.41
Nonvested as of December 31, 2011, Weighted-average grant date fair value	$ 6.41	$ 6.96
Total unrecognized compensation expense remaining	14.9
Weighted-average years expected to be recognized over	0.8
Cash-settled awards
Stock-based Compensation Nonvested Rollforward
Non-vested as of January 1, 2011	2.7
Granted	0	0.6	1.4
Vested	(0.8)
Forfeited	(0.3)
Non-vested as of December 31, 2011	1.6	2.7
Nonvested as of January 1, 2011, Weighted-average grant date fair value	$ 7.14
Granted, Weighted-average grant-date fair value	$ 8.96	$ 8.50	$ 4.43
Vested, Weighted-average grant date fair value	$ 9.76
Forfeited, Weighted-average grant date fair value	$ 7.30
Nonvested as of December 31, 2011, Weighted-average grant date fair value	$ 5.85	$ 7.14
Total unrecognized compensation expense remaining	3.7
Weighted-average years expected to be recognized over	0.7
Performance-based awards
Stock-based Compensation Nonvested Rollforward
Non-vested as of January 1, 2011	3.6
Granted	1.8	0.1	1.7
Vested	(2.5)
Forfeited	(0.9)
Non-vested as of December 31, 2011	2.0	3.6
Nonvested as of January 1, 2011, Weighted-average grant date fair value	$ 8.38
Granted, Weighted-average grant-date fair value	$ 11.58	$ 11.02	$ 6.25
Vested, Weighted-average grant date fair value	$ 9.33
Forfeited, Weighted-average grant date fair value	$ 9.72
Nonvested as of December 31, 2011, Weighted-average grant date fair value	$ 10.84	$ 8.38
Total unrecognized compensation expense remaining	12.8
Weighted-average years expected to be recognized over	1.9
Performance based cash awards settled in shares
Stock-based Compensation Nonvested Rollforward
Total unrecognized compensation expense remaining	34.5
Weighted-average years expected to be recognized over	1.8
Cash awards granted during the period target value	31.9	19.0
Time based cash awards
Stock-based Compensation Nonvested Rollforward
Cash awards granted during the period target value	4.2	31.6	28.4
Performance based cash awards
Stock-based Compensation Nonvested Rollforward
Cash awards granted during the period target value	$ 39.3	$ 18.5	$ 31.7

Target value of all cash awards granted during the period (settled in shares or cash)

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- Definition

As of the balance sheet date, the aggregate unrecognized cost of equity-based awards made to employees under equity-based compensation awards that have yet to vest.

+ References

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- Definition

The weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, using a decimal to express in number of years.

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- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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- Definition

The weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect during the reporting period as a result of the occurrence of a terminating event specified in the contractual agreement of the plan.

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- Definition

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

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- Definition

The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(2)(c)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph c(1)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(iii)(1)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(2)(a)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(2)(b)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(i)-(ii)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(2)(a)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(2)(b)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(i)-(ii)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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- Definition

The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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