Investments (Investment Income Net of Related Expenses) (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
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	$ 462,804	$ 382,503	$ 1,306,241	$ 1,277,309
Investment expense	(15,698)	(13,137)	(44,153)	(38,578)
Investment income, net of related expenses	447,106	369,366	1,262,088	1,238,731
Available-for-sale Securities [Member]
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	269,346	243,938	766,764	723,772
Mortgage Loans on Real Estate [Member]
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	39,070	33,013	102,535	89,618
Policy loans
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	13,825	15,743	41,014	49,103
Funds withheld at interest
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	124,685	80,024	345,484	376,495
Short-term Investments [Member]
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	462	374	1,507	1,609
Other invested assets
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	$ 15,416	$ 9,411	$ 48,937	$ 36,712