Schedule I - Condensed Financial Information - Schedule Of Condensed Balance Sheet (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
CURRENT ASSETS
Cash and temporary cash investments	$ 394	$ 648	$ 338	$ 260
Accounts receivable - other	1,222	1,123
Prepayments	159	145
Other current assets	232	159
TOTAL CURRENT ASSETS	3,451	3,638
Investments in subsidiaries and others	467	455
Goodwill	429	429
Other assets	10,352	10,028
TOTAL ASSETS	41,209	39,214
CURRENT LIABILITIES
Long-term debt due within one year	706	530
Notes payable	539
Accounts payable	1,215	955
Other current liabilities	542	473
TOTAL CURRENT LIABILITIES	3,945	2,987
Noncurrent Liabilities	5,689	5,831
Long-term debt	10,062	10,143
SHAREHOLDERS' EQUITY
Common stock	11,869	11,436	11,061	10,249
TOTAL SHAREHOLDERS' EQUITY	11,869	11,649
Total Liabilities and Shareholders' Equity	41,209	39,214
Parent Company [Member]
CURRENT ASSETS
Cash and temporary cash investments	4	205	222	80
Accounts receivable - other	88	93
Accounts receivable from affiliated companies	393	208
Prepayments	51	36
Other current assets	54	61
TOTAL CURRENT ASSETS	590	603
Investments in subsidiaries and others	12,672	12,145
Goodwill	406	406
Deferred income tax	20	19
Other assets	4	4
TOTAL ASSETS	13,692	13,177
CURRENT LIABILITIES
Long-term debt due within one year	2	1
Notes payable	115
Accounts payable	5	5
Accounts payable to affiliated companies	146	143
Other current liabilities	214	240
TOTAL CURRENT LIABILITIES	482	389
Noncurrent Liabilities
Total Liabilities	482	389
Long-term debt	311	313
SHAREHOLDERS' EQUITY
Common stock	4,976	4,977
Retained earnings	7,923	7,498
TOTAL SHAREHOLDERS' EQUITY	12,899	12,475
Total Liabilities and Shareholders' Equity	$ 13,692	$ 13,177