Net Investment Income Net Investment Income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Net Investment Income [Line Items]
Investment income	$ 142,224	$ 145,519	$ 313,488	$ 283,460
Investment expense	(3,495)	(1,782)	(6,048)	(3,794)
Net investment income	138,729	143,737	307,440	279,666
Fixed maturity securities, including cash and cash equivalents and loans receivable
Net Investment Income [Line Items]
Investment income	107,760	111,203	214,658	229,039
Investment funds
Net Investment Income [Line Items]
Investment income	22,356	22,576	76,155	33,510
Arbitrage trading account
Net Investment Income [Line Items]
Investment income	6,942	4,990	12,461	8,773
Equity securities available for sale
Net Investment Income [Line Items]
Investment income	2,103	3,634	4,049	5,881
Real estate
Net Investment Income [Line Items]
Investment income	$ 3,063	$ 3,116	$ 6,165	$ 6,257