Commitments and Contingent Liabilities Commitments and Contingent Liabilities (Guarantees Issued) (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Insurance Treaty Guarantee [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Current Carrying Value	$ 790,455	$ 826,496
Insurance Treaty Guarantee Net Of Assets Held In Trust [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Current Carrying Value	646,422	664,913
Guarantee Of Borrowed Securities [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Current Carrying Value	275,060	201,050
Product Financing Arrangement [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Current Carrying Value	100,000	100,000
Guarantee Of Lease Obligations [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Current Carrying Value	$ 5,245	$ 6,085