Investments (Investment Income Net of Related Expenses) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	$ 382,503	$ 406,601	$ 1,277,309	$ 1,094,696
Investment expense	(13,137)	(9,820)	(38,578)	(28,641)
Investment income, net of related expenses	369,366	396,781	1,238,731	1,066,055
Available-for-sale Securities [Member]
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	243,938	221,212	723,772	633,110
Mortgage Loans on Real Estate [Member]
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	33,013	26,938	89,618	67,258
Policy loans
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	15,743	16,519	49,103	49,637
Funds withheld at interest
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	80,024	127,855	376,495	305,861
Short-term Investments [Member]
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	374	960	1,609	3,027
Investment receivable
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	0	0	0	0
Other invested assets
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	$ 9,411	$ 13,117	$ 36,712	$ 35,803