CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenues
Net premiums	$ 9,248,871	$ 8,570,741	$ 8,669,854
Investment income, net of related expenses	1,911,886	1,734,495	1,713,691
Investment related gains (losses), net:
Other-than-temporary impairments on fixed maturity securities	(38,805)	(57,380)	(7,766)
Other-than-temporary impairments on fixed maturity securities transferred to other comprehensive income	74	0	0
Other investment related gains (losses), net	132,926	(107,370)	193,959
Total investment related gains (losses), net	94,195	(164,750)	186,193
Other revenues	266,559	277,692	334,456
Total revenues	11,521,511	10,418,178	10,904,194
Benefits and expenses
Claims and other policy benefits	7,993,375	7,489,382	7,406,641
Interest credited	364,691	336,964	451,031
Policy acquisition costs and other insurance expenses	1,310,540	1,127,486	1,391,433
Other operating expenses	645,509	554,044	538,415
Interest expense	137,623	142,863	96,700
Collateral finance and securitization expense	25,827	22,644	11,441
Total benefits and expenses	10,477,565	9,673,383	9,895,661
Income before income taxes	1,043,946	744,795	1,008,533
Provision for income taxes	342,503	242,629	324,486
Net income	$ 701,443	$ 502,166	$ 684,047
Earnings per share
Basic earnings per share (in dollars per share)	$ 10.91	$ 7.55	$ 9.88
Diluted earnings per share (in dollars per share)	10.79	7.46	9.78
Dividends declared per share	$ 1.56	$ 1.40	$ 1.26