Schedule I - Parent Company Financial Information (Condensed Balance Sheets) (Detail) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Current assets:
Cash and cash equivalents	$ 2,571	$ 1,935	$ 1,138	$ 1,306
Investment securities	7,267	7,598
Other current assets	4,712	4,007
Total current assets	15,711	15,536
Property and equipment, net	1,384	1,228
Other long-term assets	2,502	1,583
Total assets	24,705	23,527
Current liabilities:
Book overdraft	301	334
Short-term borrowings	299	0
Total current liabilities	8,152	7,471
Long-term debt	3,821	3,825
Other long-term liabilities	235	236
Total liabilities	$ 14,359	$ 13,881
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; 198,372,059 shares issued at December 31, 2015 and 197,951,551 shares issued at December 31, 2014	33	33
Capital in excess of par value	2,530	2,330
Retained earnings	11,017	9,916
Accumulated other comprehensive income	58	223
Treasury stock, at cost, 50,084,043 shares at December 31, 2015 and 48,347,541 shares at December 31, 2014	(3,292)	(2,856)
Total stockholders’ equity	10,346	9,646	9,316	8,847
Total liabilities and stockholders’ equity	24,705	23,527
Parent Company
Current assets:
Cash and cash equivalents	1,389	1,211	$ 161	$ 151
Investment securities	256	201
Receivable from operating subsidiaries	1,124	873
Other current assets	224	180
Total current assets	2,993	2,465
Property and equipment, net	1,011	885
Investments in subsidiaries	14,276	13,983
Other long-term assets	437	114
Total assets	18,717	17,447
Current liabilities:
Payable to operating subsidiaries	3,322	3,130
Current portion of notes payable to operating subsidiaries	28	28
Book overdraft	38	54
Short-term borrowings	299	0
Other current liabilities	572	562
Total current liabilities	4,259	3,774
Long-term debt	3,821	3,825
Notes payable to operating subsidiaries	9	9
Other long-term liabilities	282	193
Total liabilities	8,371	7,801
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; 198,372,059 shares issued at December 31, 2015 and 197,951,551 shares issued at December 31, 2014	33	33
Capital in excess of par value		2,330
Retained earnings		9,916
Accumulated other comprehensive income		223
Treasury stock, at cost, 50,084,043 shares at December 31, 2015 and 48,347,541 shares at December 31, 2014	(3,292)	(2,856)
Total stockholders’ equity	10,346	9,646
Total liabilities and stockholders’ equity	$ 18,717	$ 17,447