MEDICARE PART D (Detail) - USD ($) $ in Millions	Nov. 01, 2016	Sep. 30, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Other current assets		$ 4,791	$ 4,712
Trade accounts payable and accrued expenses		(2,933)	(2,212)
Other long-term assets		2,789	2,475
Other long-term liabilities		(279)	(235)
Risk Corridor Settlement
Segment Reporting Information [Line Items]
Other current assets		41	25
Trade accounts payable and accrued expenses		(43)	(47)
Net current (liability) asset		(2)	(22)
Other long-term assets		6	0
Other long-term liabilities		(40)	0
Net long-term asset		(34)	0
Total net (liability) asset		(36)	(22)
CMS Subsidies/ Discounts
Segment Reporting Information [Line Items]
Other current assets		2,287	2,082
Trade accounts payable and accrued expenses		(672)	(63)
Net current (liability) asset		1,615	2,019
Other long-term assets		0	0
Other long-term liabilities		0	0
Net long-term asset		0	0
Total net (liability) asset		$ 1,615	$ 2,019
Subsequent Event | CMS Subsidies/ Discounts
Segment Reporting Information [Line Items]
Settlement collected	$ 2,000