Net Investment Income Net Investment Income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Net Investment Income [Line Items]
Investment income	$ 180,824	$ 127,541	$ 494,312	$ 411,001
Investment expense	(1,599)	(1,907)	(7,647)	(5,701)
Net investment income	179,225	125,634	486,665	405,300
Fixed maturity securities, including cash and cash equivalents and loans receivable
Net Investment Income [Line Items]
Investment income	117,289	104,033	331,947	333,072
Investment funds
Net Investment Income [Line Items]
Investment income	59,077	5,492	135,232	45,248
Arbitrage trading account
Net Investment Income [Line Items]
Investment income	47	11,738	12,508	14,265
Equity securities available for sale
Net Investment Income [Line Items]
Investment income	1,369	3,192	5,418	9,073
Real estate
Net Investment Income [Line Items]
Investment income	$ 3,042	$ 3,086	$ 9,207	$ 9,343