Investments (Investment Income Net of Related Expenses) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	$ 424,740	$ 457,415	$ 843,437	$ 894,806
Investment expense	(14,133)	(13,181)	(28,455)	(25,441)
Investment income, net of related expenses	410,607	444,234	814,982	869,365
Available-for-sale Securities [Member]
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	253,456	240,590	497,418	479,834
Mortgage Loans on Real Estate [Member]
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	30,373	28,362	63,465	56,605
Policy loans
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	13,751	15,450	27,189	33,360
Funds withheld at interest
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	108,059	159,212	220,798	296,471
Short-term Investments [Member]
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	80	422	1,045	1,235
Other invested assets
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	$ 19,021	$ 13,379	$ 33,522	$ 27,301