Schedule I - Parent Company Financial Information (Condensed Balance Sheets) (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Current assets:
Cash and cash equivalents	$ 3,877	$ 2,571	$ 1,935	$ 1,138
Investment securities	7,595	7,267
Other current assets	3,438	4,712
Total current assets	16,190	15,711
Property and equipment, net	1,505	1,384
Other long-term assets	2,226	2,475
Total assets	25,396	24,678
Current liabilities:
Book overdraft	212	301
Short-term borrowings	300	299
Total current liabilities	7,822	8,152
Long-term debt	3,792	3,794
Other long-term liabilities	263	235
Total liabilities	14,711	14,332
Commitments and contingencies
Stockholders’ equity:
Preferred stock, $1 par; 10,000,000 shares authorized; none issued	0	0
Common stock, $0.16 2/3 par; 300,000,000 shares authorized; 198,495,007 shares issued at December 31, 2016 and 198,372,059 shares issued at December 31, 2015	33	33
Capital in excess of par value	2,562	2,530
Retained earnings	11,454	11,017
Accumulated other comprehensive (loss) income	(66)	58
Treasury stock, at cost, 49,189,811 shares at December 31, 2016 and 50,084,043 shares at December 31, 2015	(3,298)	(3,292)
Total stockholders’ equity	10,685	10,346	9,646	9,316
Total liabilities and stockholders’ equity	25,396	24,678
Parent Company
Current assets:
Cash and cash equivalents	1,710	1,389	$ 1,211	$ 161
Investment securities	300	256
Receivable from operating subsidiaries	1,136	1,124
Other current assets	122	224
Total current assets	3,268	2,993
Property and equipment, net	1,086	1,011
Investments in subsidiaries	15,276	14,276
Other long-term assets	374	410
Total assets	20,004	18,690
Current liabilities:
Payable to operating subsidiaries	4,107	3,322
Current portion of notes payable to operating subsidiaries	28	28
Book overdraft	38	38
Short-term borrowings	300	299
Other current liabilities	708	572
Total current liabilities	5,181	4,259
Long-term debt	3,792	3,794
Notes payable to operating subsidiaries	9	9
Other long-term liabilities	337	282
Total liabilities	9,319	8,344
Stockholders’ equity:
Preferred stock, $1 par; 10,000,000 shares authorized; none issued	0	0
Common stock, $0.16 2/3 par; 300,000,000 shares authorized; 198,495,007 shares issued at December 31, 2016 and 198,372,059 shares issued at December 31, 2015	33	33
Capital in excess of par value	2,562	2,530
Retained earnings		11,017
Accumulated other comprehensive (loss) income	(66)	58
Treasury stock, at cost, 49,189,811 shares at December 31, 2016 and 50,084,043 shares at December 31, 2015	(3,298)	(3,292)
Total stockholders’ equity	10,685	10,346
Total liabilities and stockholders’ equity	$ 20,004	$ 18,690