Investment Securities (Restrictions on Redemption Frequency and Advance Notice Requirements) (Details) (Hedge funds, USD $) In Millions, unless otherwise specified	Mar. 31, 2015
Schedule of Trading Securities and Other Trading Assets [Line Items]
Distributions from Inactive Hedge Funds	$ 2.1
Other long-term investments	92.1
Redemption requests	6.9
30-59 days notice
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other long-term investments	36.3
Fair Value Investments Entities that Calculate Net Asset Value Per Share Investment Redemption Notice Period60 To89 Days [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other long-term investments	43.0
Fair Value Investments Entities that Calculate Net Asset Value Per Share Investment Redemption Notice Period90 To119 Days [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other long-term investments	4.7
120+ days notice
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other long-term investments	8.1
Monthly
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other long-term investments	4.5
Monthly | 30-59 days notice
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other long-term investments	4.5
Monthly | Fair Value Investments Entities that Calculate Net Asset Value Per Share Investment Redemption Notice Period60 To89 Days [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other long-term investments	0
Monthly | Fair Value Investments Entities that Calculate Net Asset Value Per Share Investment Redemption Notice Period90 To119 Days [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other long-term investments	0
Monthly | 120+ days notice
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other long-term investments	0
Quarterly
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other long-term investments	59.8
Quarterly | 30-59 days notice
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other long-term investments	31.8
Quarterly | Fair Value Investments Entities that Calculate Net Asset Value Per Share Investment Redemption Notice Period60 To89 Days [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other long-term investments	20.1
Quarterly | Fair Value Investments Entities that Calculate Net Asset Value Per Share Investment Redemption Notice Period90 To119 Days [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other long-term investments	0
Quarterly | 120+ days notice
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other long-term investments	7.9
Semi-annual
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other long-term investments	22.9
Semi-annual | 30-59 days notice
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other long-term investments	0
Semi-annual | Fair Value Investments Entities that Calculate Net Asset Value Per Share Investment Redemption Notice Period60 To89 Days [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other long-term investments	22.9
Semi-annual | Fair Value Investments Entities that Calculate Net Asset Value Per Share Investment Redemption Notice Period90 To119 Days [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other long-term investments	0
Semi-annual | 120+ days notice
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other long-term investments	0
Annual
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other long-term investments	4.9
Annual | 30-59 days notice
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other long-term investments	0
Annual | Fair Value Investments Entities that Calculate Net Asset Value Per Share Investment Redemption Notice Period60 To89 Days [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other long-term investments	0
Annual | Fair Value Investments Entities that Calculate Net Asset Value Per Share Investment Redemption Notice Period90 To119 Days [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other long-term investments	4.7
Annual | 120+ days notice
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other long-term investments	$ 0.2