Commitments, Contingencies And Guarantees (External Credit Ratings Of Underlying Or Referenced Assets For Credit Related Derivatives Contracts) (Details) $ in Millions	Dec. 31, 2015 USD ($)
Below Investment Grade [Member] | Index credit default swaps [Member]
Guarantor Obligations [Line Items]
Credit Related Derivative Contracts by External Credit Ratings	$ 0.0
Below Investment Grade [Member] | Single name credit default swaps [Member]
Guarantor Obligations [Line Items]
Credit Related Derivative Contracts by External Credit Ratings	264.3
AAA/Aaa [Member] | Index credit default swaps [Member]
Guarantor Obligations [Line Items]
Credit Related Derivative Contracts by External Credit Ratings	698.4
AAA/Aaa [Member] | Single name credit default swaps [Member]
Guarantor Obligations [Line Items]
Credit Related Derivative Contracts by External Credit Ratings	0.0
AA/Aa [Member] | Index credit default swaps [Member]
Guarantor Obligations [Line Items]
Credit Related Derivative Contracts by External Credit Ratings	0.0
AA/Aa [Member] | Single name credit default swaps [Member]
Guarantor Obligations [Line Items]
Credit Related Derivative Contracts by External Credit Ratings	0.0
A [Member] | Index credit default swaps [Member]
Guarantor Obligations [Line Items]
Credit Related Derivative Contracts by External Credit Ratings	0.0
A [Member] | Single name credit default swaps [Member]
Guarantor Obligations [Line Items]
Credit Related Derivative Contracts by External Credit Ratings	10.0
BBB/Baa [Member] | Index credit default swaps [Member]
Guarantor Obligations [Line Items]
Credit Related Derivative Contracts by External Credit Ratings	0.0
BBB/Baa [Member] | Single name credit default swaps [Member]
Guarantor Obligations [Line Items]
Credit Related Derivative Contracts by External Credit Ratings	57.5
Unrated [Member] | Index credit default swaps [Member]
Guarantor Obligations [Line Items]
Credit Related Derivative Contracts by External Credit Ratings	0.0
Unrated [Member] | Single name credit default swaps [Member]
Guarantor Obligations [Line Items]
Credit Related Derivative Contracts by External Credit Ratings	50.6
Notional/Maximum Payout [Member] | Index credit default swaps [Member]
Guarantor Obligations [Line Items]
Notional/ Maximum Payout	698.4
Notional/Maximum Payout [Member] | Single name credit default swaps [Member]
Guarantor Obligations [Line Items]
Notional/ Maximum Payout	$ 382.4