Quarterly Results of Operations (Unaudited) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Notes to Financial Statements [Abstract]
Total revenues	$ 2,964	$ 2,954	$ 2,899	$ 2,715	$ 2,569	$ 2,547	$ 2,807	$ 2,718	$ 11,532	$ 10,641	$ 10,415
Total expenses	2,564	2,536	2,457	2,407	3,058	2,393	2,399	2,288	9,964	10,138	9,280
Income (loss) from continuing operations	320	400	322	244	(541)	158	301	311	1,286	229	873
Income (loss) from discontinued operations, net of federal income tax expense (benefit)	0	28	0	(1)	0	(8)	0	0	27	(8)	29
Net income (loss)	320	428	322	243	(541)	150	301	311	1,313	221	902
Earnings (loss) per common share - basic:
Income (loss) from continuing operations (in dollars per share)	$ 1.17	$ 1.44	$ 1.14	$ 0.84	$ (1.82)	$ 0.52	$ 0.97	$ 0.99	$ 4.58	$ 0.75	$ 2.28
Income (loss) from discontinued operations (in dollars per share)	$ 0	$ 0.10	$ 0	$ 0	$ 0	$ (0.03)	$ 0	$ 0	$ 0.10	$ (0.03)	$ 0.09
Net income (loss) (in dollars per share)	$ 1.17	$ 1.54	$ 1.14	$ 0.84	$ (1.82)	$ 0.49	$ 0.97	$ 0.99	$ 4.68	$ 0.72	$ 2.37
Earnings (loss) per common share - diluted:
Income (loss) from continuing operations (in dollars per share)	$ 1.14	$ 1.41	$ 1.09	$ 0.82	$ (1.82)	$ 0.49	$ 0.94	$ 0.96	$ 4.47	$ 0.72	$ 2.21
Income (loss) from discontinued operations (in dollars per share)	$ 0	$ 0.10	$ 0	$ 0	$ 0	$ (0.03)	$ 0	$ 0	$ 0.09	$ (0.03)	$ 0.09
Net income (loss) (in dollars per share)	$ 1.14	$ 1.51	$ 1.09	$ 0.82	$ (1.82)	$ 0.46	$ 0.94	$ 0.96	$ 4.56	$ 0.69	$ 2.30
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Net income (loss)	320	428	322	243	(541)	150	301	311	1,313	221	902
Income (loss) from continuing operations	320	400	322	244	(541)	158	301	311	1,286	229	873
Other liabilities	5,139				4,410				5,139	4,410
Liabilities	203,896				188,390				203,896	188,390
Retained earnings	4,044				2,831				4,044	2,831
Total stockholders' equity	14,973				13,101				14,973	13,101	11,686
Income Tax Expense (Benefit)									282	274	262
Tax Error [Member]
Notes to Financial Statements [Abstract]
Income (loss) from continuing operations		27	(3)	(3)	(3)	(3)	(3)	(3)
Net income (loss)		27	(3)	(3)	(3)	(3)	(3)	(3)
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Net income (loss)		27	(3)	(3)	(3)	(3)	(3)	(3)
Income (loss) from continuing operations		27	(3)	(3)	(3)	(3)	(3)	(3)
Other liabilities		117	144	141	138	136	133	130		138
Liabilities		117	144	141	138	136	133	130		138
Retained earnings		(117)	(144)	(141)	(138)	(136)	(133)	(130)		(138)
Total stockholders' equity		(117)	(144)	(141)	(138)	(136)	(133)	(130)		(138)
Earnings Per Share, Basic and Diluted		$ 0.1	$ (0.01)	$ (0.01)	$ (0.01)	$ (0.01)	$ (0.01)	$ (0.01)
Income Tax Expense (Benefit)		$ (3)	$ 3	$ 3	$ 3	$ 3	$ 3	$ 3