Commitments, Contingencies and Guarantees (Guarantees Issued) (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Insurance Treaty Guarantee [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Current Carrying Value	$ 797,246	$ 765,505
Insurance Treaty Guarantee Net Of Assets Held In Trust [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Current Carrying Value	663,575	634,909
Guarantee Of Borrowed Securities [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Current Carrying Value	268,800	259,540
Product Financing Arrangement [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Current Carrying Value	0	100,000
Guarantee Of Lease Obligations [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Current Carrying Value	$ 3,650	$ 5,217