CONSOLIDATED STATEMENTS OF INCOME (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Revenues
Premiums and policy fees	$ 837,706	$ 653,664	$ 752,752	$ 723,200	$ 717,948	$ 681,324	$ 707,720	$ 692,398	$ 2,967,322	$ 2,799,390	$ 2,784,134
Reinsurance ceded	(387,192)	(277,628)	(396,777)	(325,840)	(365,821)	(311,862)	(336,119)	(296,295)	(1,387,437)	(1,310,097)	(1,363,914)
Net of reinsurance ceded	450,514	376,036	355,975	397,360	352,127	369,462	371,601	396,103	1,579,885	1,489,293	1,420,220
Net investment income	515,340	434,772	447,064	439,012	460,784	446,374	438,648	443,532	1,836,188	1,789,338	1,753,444
Realized investment gains (losses):
Derivative financial instruments									82,161	(227,816)	(155,005)
All other investments									(121,537)	232,836	247,753
Other-than-temporary impairment losses									(10,941)	(67,130)	(62,210)
Portion recognized in other comprehensive income (before taxes)									(11,506)	8,986	14,889
Net impairment losses recognized in earnings									(22,447)	(58,144)	(47,321)
Other income	69,825	65,523	60,638	54,434	54,244	51,046	50,121	75,142	250,420	230,553	189,494
Total revenues	1,022,452	880,594	816,041	885,583	823,070	864,196	867,039	901,755	3,604,670	3,456,060	3,408,585
Benefits and expenses
Benefits and settlement expenses, net of reinsurance ceded: (2013 - $1,207,781; 2012 - $1,228,897; 2011 - $1,231,405)									2,473,988	2,317,121	2,222,220
Amortization of deferred policy acquisition costs and value of business acquired									154,660	192,183	249,520
Other operating expenses, net of reinsurance ceded: (2013 - $199,079; 2012 - $200,442; 2011 - $203,868)									553,523	487,177	461,570
Total benefits and expenses	902,049	767,239	737,114	775,769	728,313	757,507	749,974	760,687	3,182,171	2,996,481	2,933,310
Income before income tax	120,403	113,355	78,927	109,814	94,757	106,689	117,065	141,068	422,499	459,579	475,275
Income tax (benefit) expense
Current									(18,298)	81,006	(4,576)
Deferred									149,195	70,037	156,095
Total income tax expense	31,931	37,107	25,923	35,936	34,615	35,778	35,438	45,212	130,897	151,043	151,519
Net income	$ 88,472	$ 76,248	$ 53,004	$ 73,878	$ 60,142	$ 70,911	$ 81,627	$ 95,856	$ 291,602	$ 308,536	$ 323,756