CONSOLIDATED STATEMENTS OF INCOME (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Revenues:
Net premiums	$ 7,906,596,000	$ 7,335,687,000	$ 6,659,680,000
Investment income, net of related expenses	1,436,206,000	1,281,197,000	1,238,660,000
Investment related gains (losses), net:
Other-than-temporary impairments on fixed maturity securities	(15,908,000)	(30,873,000)	(31,920,000)
Other-than-temporary impairments on fixed maturity securities transferred to (from) accumulated other comprehensive income	7,618,000	(3,924,000)	(2,045,000)
Other investment related gains (losses), net	277,662,000	(9,107,000)	241,905,000
Total investment related gains (losses), net	254,136,000	(36,056,000)	212,030,000
Other revenues	243,973,000	248,710,000	151,360,000
Total revenues	9,840,911,000	8,829,538,000	8,261,730,000
Benefits and Expenses:
Claims and other policy benefits	6,665,999,000	6,225,183,000	5,547,155,000
Interest credited	379,915,000	316,394,000	309,982,000
Policy acquisition costs and other insurance expenses	1,306,470,000	990,021,000	1,137,589,000
Other operating expenses	451,759,000	419,340,000	361,971,000
Interest expense	105,348,000	102,638,000	90,996,000
Collateral finance facility expense	12,197,000	12,391,000	7,856,000
Total benefits and expenses	8,921,688,000	8,065,967,000	7,455,549,000
Income before income taxes	919,223,000	763,571,000	806,181,000
Provision for income taxes	(287,330,000)	(217,526,000)	(270,439,000)
Net income	$ 631,893,000	$ 546,045,000	$ 535,742,000
Basic earnings per share:
Income from continuing operations basic earnings per share	$ 8.57	$ 7.42	$ 7.32
Diluted earnings per share:
Income from continuing operations diluted earnings per share	$ 8.52	$ 7.37	$ 7.17
Dividends declared per share	$ 0.84	$ 0.60	$ 0.48