Investment Securities (Net unrealized investment gains and losses) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Schedule of Investments [Abstract]
Trading Securities Gross Unrealized Gain	$ 142.7	$ 133.7
Trading Securities Gross Unrealized Loss	(6.7)	(9.3)
Gross Unrealized Gains (Losses) on Trading Securities Pretax	136.0	124.4
Deferred Tax Liabilities, Unrealized Gains on Trading Securities	(37.3)	(33.8)
Unrealized gains (losses) on trading securities, net of tax	$ 98.7	$ 90.6

Amount of deferred tax liability attributable to taxable temporary differences from unrealized gains on trading securities.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 50

-Paragraph 6

-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32621-109319

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 25

-Paragraph 20

-URI http://asc.fasb.org/extlink&oid=29652012&loc=d3e28680-109314

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 50

-Paragraph 8

-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32632-109319

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