Investments Investment Income (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Net Investment Income [Line Items]
Net investment income	$ 108,000	$ 117,000	$ 120,000	$ 105,000	$ 115,000	$ 118,000	$ 130,000	$ 117,000	$ 449,784	$ 479,696	$ 484,367
Trading securities [Member] | Fixed maturities
Net Investment Income [Line Items]
Net investment income									425,541	443,414	446,299
Trading securities [Member] | Short Term Investments, Cash And Cash Equivalents[Member]
Net Investment Income [Line Items]
Net investment income									854	868	1,886
Trading securities [Member] | Equities
Net Investment Income [Line Items]
Net investment income									30,739	40,326	32,989
Trading securities [Member] | Funds Held And Other [Member]
Net Investment Income [Line Items]
Net investment income									27,406	33,192	34,215
Trading securities [Member] | Funds Held - Directly Managed [Member]
Net Investment Income [Line Items]
Net investment income									11,676	13,841	20,502
Trading securities [Member] | Investment Expenses [Member]
Net Investment Income [Line Items]
Net investment income									$ (46,432)	$ (51,945)	$ (51,524)