Schedule I-Parent Company Financial Information (Condensed Balance Sheets) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Cash and cash equivalents	$ 1,377	$ 1,673	$ 1,613	$ 1,970
Investment securities	7,743	6,873
Other current assets	1,027.0	632.0
Total current assets	11,181	10,137
Property and equipment, net	912	815
Other long-term assets	1,165	1,083
Total assets	17,708	16,103
Book overdraft	306	409
Total current liabilities	6,056	5,744
Long-term debt	1,659	1,669
Other long-term liabilities	267	273
Total liabilities	9,645	9,179
Commitments and contingencies
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; 193,230,310 shares issued in 2011 and 190,244,741 shares issued in 2010	32	32
Capital in excess of par value	1,938	1,737
Retained earnings	6,825	5,529
Accumulated other comprehensive income	303	120
Treasury stock, at cost, 29,225,996 shares in 2011 and 21,795,051 shares in 2010	(1,035)	(494)
Total stockholders' equity	8,063	6,924	5,776	4,457
Total liabilities and stockholders' equity	17,708	16,103
Parent Company [Member]
Cash and cash equivalents	187	314	346	249
Investment securities	307	239
Receivable from operating subsidiaries	572	494
Other current assets	75.0	56.0
Total current assets	1,141	1,103
Property and equipment, net	543	479
Investments in subsidiaries	9,971	8,759
Other long-term assets	55	36
Total assets	11,710	10,377
Payable to operating subsidiaries	1,364	1,241
Current portion of notes payable to operating subsidiaries	28	28
Book overdraft	44	65
Other current liabilities	400	366
Total current liabilities	1,836	1,700
Long-term debt	1,623	1,633
Notes payable to operating subsidiaries	9	9
Other long-term liabilities	179	111
Total liabilities	3,647	3,453
Commitments and contingencies
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; 193,230,310 shares issued in 2011 and 190,244,741 shares issued in 2010	32	32
Capital in excess of par value	1,938	1,737
Retained earnings	6,825	5,529
Accumulated other comprehensive income	303	120
Treasury stock, at cost, 29,225,996 shares in 2011 and 21,795,051 shares in 2010	(1,035)	(494)
Total stockholders' equity	8,063	6,924
Total liabilities and stockholders' equity	$ 11,710	$ 10,377