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Investment Securities (Fair Value of Hedge Funds Subject to Restrictions on Redemption Frequency) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012		Mar. 31, 2012	Dec. 31, 2011
Hedge funds
Investment securities
Other long-term investments	$ 117.7
Private equity funds
Investment securities
Other long-term investments	122.1
Hedge and private equity funds included in other long-term investments
Investment securities
Other long-term investments	239.8	[1]	239.8	[1]
Carrying value excluded associated with hedge funds and private equity funds	134.9	[1]	133.4	[1]
Hedge funds | Hedge Funds, Equity
Investment securities
Other long-term investments	60.0		60.3
Carrying value excluded associated with hedge funds and private equity funds	0		0
Hedge funds | Hedge Funds Credit and Distressed
Investment securities
Other long-term investments	24.5		22.7
Carrying value excluded associated with hedge funds and private equity funds	0		0
Hedge funds | Hedge Funds Diversified Strategies
Investment securities
Other long-term investments	1.7		1.7
Carrying value excluded associated with hedge funds and private equity funds	0		0
Hedge funds | Hedge Funds Equity R E I T
Investment securities
Other long-term investments	16.7		16.0
Carrying value excluded associated with hedge funds and private equity funds	0		0
Hedge funds | Hedge Funds Equity Activist
Investment securities
Other long-term investments	14.5		13.6
Carrying value excluded associated with hedge funds and private equity funds	0		0
Hedge funds | Hedge Funds Bank Loan
Investment securities
Other long-term investments	0.3		0.3
Carrying value excluded associated with hedge funds and private equity funds	0		0
Hedge funds | Hedge funds
Investment securities
Other long-term investments	117.7		114.6
Carrying value excluded associated with hedge funds and private equity funds	0		0
Private equity funds | Private Equity Multi Sector
Investment securities
Other long-term investments	25.9		23.3
Carrying value excluded associated with hedge funds and private equity funds	8.9		5.4
Private equity funds | Private Equity Energy Infrastructure and Services
Investment securities
Other long-term investments	35.0		36.3
Carrying value excluded associated with hedge funds and private equity funds	14.8		15.6
Private equity funds | Private Equity Distressed Residential Real Estate
Investment securities
Other long-term investments	14.6		15.8
Carrying value excluded associated with hedge funds and private equity funds	0		0
Private equity funds | Real Estate Funds
Investment securities
Other long-term investments	10.9		11.6
Carrying value excluded associated with hedge funds and private equity funds	3.3		3.3
Private equity funds | Private Equity Secondaries
Investment securities
Other long-term investments	10.6		10.5
Carrying value excluded associated with hedge funds and private equity funds	3.1		3.1
Private equity funds | Private Equity Funds Multi Sector Europe
Investment securities
Other long-term investments	4.2		5.1
Carrying value excluded associated with hedge funds and private equity funds	5.0		5.0
Private equity funds | Private Equity Funds Manufacturing and Industrial
Investment securities
Other long-term investments	9.0		9.9
Carrying value excluded associated with hedge funds and private equity funds	28.7		29.1
Private equity funds | Private Equity Healthcare
Investment securities
Other long-term investments	4.2		4.3
Carrying value excluded associated with hedge funds and private equity funds	5.0		5.4
Private equity funds | Private Equity Funds Multi Sector Asia
Investment securities
Other long-term investments	0		0.4
Carrying value excluded associated with hedge funds and private equity funds	2.7		2.7
Private equity funds | Private Equity Insurance
Investment securities
Other long-term investments	2.5		3.0
Carrying value excluded associated with hedge funds and private equity funds	41.3		41.3
Private equity funds | Aerospace Defense Government
Investment securities
Other long-term investments	3.0		2.8
Carrying value excluded associated with hedge funds and private equity funds	21.8		22.2
Private equity funds | Venture Capital Funds
Investment securities
Other long-term investments	2.2		2.2
Carrying value excluded associated with hedge funds and private equity funds	0.3		0.3
Private equity funds | Private equity funds
Investment securities
Other long-term investments	122.1		125.2
Carrying value excluded associated with hedge funds and private equity funds	134.9		133.4
Level 3 Inputs | Fair value measured on a recurring basis | Other long-term investments
Investment securities
Carrying value of investment accounted for using the equity method	$ 34.9		$ 35.0		$ 33.0	$ 33.2
[1] Excludes carrying value of $35.0 and $34.9 at January 1, 2013 and March 31, 2013 associated with hedge funds and private equity funds accounted for using the equity method.

X

- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents investments accounted for under the equity method of accounting as of the balance sheet date.

+ References

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

-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 18

-Paragraph 6

-Subparagraph 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 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 323

-SubTopic 10

-Section 25

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6903542&loc=d3e32014-111567

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X

- Definition

The amount of unfunded commitments for which the entity is obligated, to those certain investments for which net asset value per share is calculated (including by unit, membership interest, or other equity (ownership interest) unit measure) (alternative investments).

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 6A

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=7578670&loc=SL6742756-110258

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X

- Definition

This element represents the total fair market value of investments in certain entities that calculate net asset value per share (including by unit, membership interest, or other equity (ownership interest) unit measure) (alternative investments). This element is intended to be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements, but may also be used in both the balance sheet and disclosure in the same submission. This item represents alternative investments as of the balance sheet date which may include investments in certain hedge funds, venture capital funds, private equity funds, real estate partnerships or funds, and any other investment in which investee management calculates net asset value per share as the primary metric for investment value.

+ References

No definition available.

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