Investments (Investment Income Net of Related Expenses) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	$ 418,697	$ 437,391
Investment expense	(14,322)	(12,260)
Investment income, net of related expenses	404,375	425,131
Available-for-sale Securities [Member]
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	243,962	239,244
Mortgage Loans on Real Estate [Member]
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	33,092	28,243
Policy loans
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	13,438	17,910
Funds withheld at interest
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	112,739	137,259
Short-term Investments [Member]
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	965	813
Other invested assets
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	$ 14,501	$ 13,922