Quarterly Results of Operations (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended												12 Months Ended
	Dec. 31, 2016		Sep. 30, 2016		Jun. 30, 2016		Mar. 31, 2016		Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Total revenues	$ 3,255		$ 3,525		$ 3,307		$ 3,243		$ 3,171	$ 3,716	$ 3,381	$ 3,304	$ 13,330	$ 13,572	$ 13,554
Total expenses	3,058		2,913		2,893		3,008		2,820	3,448	2,932	2,942	11,872	12,142	11,557
Income (loss) from continuing operations													1,192	1,154	1,514
Income (loss) from discontinued operations, net of federal income tax expense (benefit)															1
Net income (loss)	$ 189	[1]	$ 467	[1]	$ 325	[1]	$ 211	[1]	$ 283	$ 227	$ 344	$ 300	$ 1,192	$ 1,154	$ 1,515
Earnings (loss) per common share - basic:
Income (loss) from continuing operations (in dollars per share)													$ 5.09	$ 4.60	$ 5.81
Income (loss) from discontinued operations (in dollars per share)
Net income (loss) (in dollars per share)	$ 0.83	[1]	$ 2.02	[1]	$ 1.37	[1]	$ 0.87	[1]	$ 1.15	$ 0.91	$ 1.37	$ 1.17	5.09	4.60	5.81
Earnings (loss) per common share - diluted:
Income (loss) from continuing operations (in dollars per share)													5.03	4.51	5.67
Income (loss) from discontinued operations (in dollars per share)
Net income (loss) (in dollars per share)	$ 0.82	[1]	$ 2.00	[1]	$ 1.35	[1]	$ 0.83	[1]	$ 1.14	$ 0.87	$ 1.35	$ 1.15	$ 5.03	$ 4.51	$ 5.67
Parent Company [Member]
Total revenues													$ 1,161	$ 1,311	$ 918
Total expenses													389	315	325
Net income (loss)													$ 1,192	$ 1,154	$ 1,515

[1] Effective October 1, 2016, we early adopted ASU 2016-09, Improvements to Employee Share-Based Payment Accounting. We have updated certain previously reported interim results and metrics as of January 1, 2016, in accordance with the new guidance. For more information, see Note 2.