Net Investment Income (Net Investment Income) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Net Investment Income [Line Items]
Gross investment income	$ 554,308	$ 592,852	$ 529,820
Investment expense	(10,017)	(6,089)	(3,469)
Net investment income	544,291	586,763	526,351
Fixed maturity securities, including cash and cash equivalents and loans receivable
Net Investment Income [Line Items]
Gross investment income	442,287	479,035	483,905
Equity securities available for sale
Net Investment Income [Line Items]
Gross investment income	11,380	16,419	12,416
Investment funds
Net Investment Income [Line Items]
Gross investment income	67,712	77,015	9,452
Arbitrage trading account
Net Investment Income [Line Items]
Gross investment income	20,431	8,286	16,576
Real estate
Net Investment Income [Line Items]
Gross investment income	$ 12,498	$ 12,097	$ 7,471