QUARTERLY FINANCIAL INFORMATION (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
Quarterly Financial Information Disclosure [Abstract]
Total revenues	$ 12,878	$ 13,694	$ 14,007	$ 13,800	$ 13,361	$ 13,363	$ 13,732	$ 13,833	$ 54,379	$ 54,289	$ 48,500
Income (loss) before income taxes	(486)	902	636	500	246	648	793	744	1,552	2,431	2,170
Net income	$ (401)	$ 450	$ 311	$ 254	$ 101	$ 314	$ 431	$ 430	$ 614	$ 1,276	$ 1,147
Basic earnings (loss) per common share (in dollars per share)	$ (2.68)	$ 3.01	$ 2.08	$ 1.70	$ 0.68	$ 2.11	$ 2.88	$ 2.86	$ 4.11	$ 8.54	$ 7.44
Diluted earnings (loss) per common share (in dollars per share)	$ (2.68)	$ 2.98	$ 2.06	$ 1.68	$ 0.67	$ 2.09	$ 2.85	$ 2.82	$ 4.07	$ 8.44	$ 7.36
Long-term insurance reserve strengthening expense	$ 505
Long-term insurance reserve strengthening expense, net of tax	$ 318
Long-term insurance reserve strengthening expense, per diluted share (in dollars per share)	$ 2.11
Premiums reduction, write off of risk corridor receivables									$ 583
Premiums reduction, write off of risk corridor receivables, net of tax									$ 367
Premiums reduction, write off of risk corridor receivables, per diluted share (in dollars per share)									$ 2.43
Provision for premium deficiency					$ 176				$ (176)	$ 176	$ 0
Provision for premium deficiency, net					$ 112
Provision for premium deficiency, per diluted share (in dollars per share)					$ 0.74
Benefit expense with future policy benefits payable									$ 439	$ (80)	$ 32