Investment Securities (Restrictions on Redemption Frequency and Advance Notice Requirements) (Details) - Hedge funds $ in Millions	Jun. 30, 2015 USD ($)
Schedule of Trading Securities and Other Trading Assets [Line Items]
Distributions from Inactive Hedge Funds	$ 2.0
Other long-term investments	77.7
Redemption requests	10.2
30-59 days notice
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other long-term investments	23.0
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	41.7
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	4.9
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	5.2
Monthly | 30-59 days notice
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other long-term investments	5.2
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	0.0
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	0.0
Monthly | 120+ days notice
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other long-term investments	0.0
Quarterly
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other long-term investments	45.0
Quarterly | 30-59 days notice
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other long-term investments	17.8
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	19.2
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	0.0
Quarterly | 120+ days notice
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other long-term investments	8.0
Semi-annual
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other long-term investments	22.5
Semi-annual | 30-59 days notice
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other long-term investments	0.0
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	22.5
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	0.0
Semi-annual | 120+ days notice
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other long-term investments	0.0
Annual
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other long-term investments	5.0
Annual | 30-59 days notice
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other long-term investments	0.0
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	0.0
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	4.9
Annual | 120+ days notice
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other long-term investments	$ 0.1