Investments Income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Net Investment Income [Line Items]
Net investment income	$ 115,000	$ 118,000	$ 130,000	$ 117,000	$ 114,000	$ 122,000	$ 125,000	$ 124,000	$ 479,696	$ 484,367	$ 571,338
Trading securities [Member] | Fixed maturities
Net Investment Income [Line Items]
Net investment income									443,414	446,299	512,833
Trading securities [Member] | Short Term Investments, Cash And Cash Equivalents[Member]
Net Investment Income [Line Items]
Net investment income									868	1,886	2,905
Trading securities [Member] | Equities
Net Investment Income [Line Items]
Net investment income									40,326	32,989	26,207
Trading securities [Member] | Funds Held And Other [Member]
Net Investment Income [Line Items]
Net investment income									33,192	34,215	44,109
Trading securities [Member] | Funds Held - Directly Managed [Member]
Net Investment Income [Line Items]
Net investment income									13,841	20,502	29,031
Trading securities [Member] | Investment Expenses [Member]
Net Investment Income [Line Items]
Net investment income									$ (51,945)	$ (51,524)	$ (43,747)