Equity - Changes in Shares of Common Stock (Detail)	12 Months Ended						12 Months Ended
Equity - Changes in Shares of Common Stock (Detail)	Dec. 31, 2011 Issued [Member]	Dec. 31, 2010 Issued [Member]	Dec. 31, 2009 Issued [Member]	Dec. 31, 2011 Held In Treasury [Member]	Dec. 31, 2010 Held In Treasury [Member]	Dec. 31, 2008 Held In Treasury [Member]	Dec. 31, 2011 Held in Grantor Trusts [Member]	Dec. 31, 2010 Held in Grantor Trusts [Member]	Dec. 31, 2009 Held in Grantor Trusts [Member]
Beginning balance, Common stock	1,740,529,279	1,733,345,558	1,729,264,859	272,873,537	208,346,815	208,346,815	36,890,375	38,742,261	40,739,129
Repurchase of common stock				155,453,382	64,526,722		(157,470)
Distributed under benefit plans	9,021,308	7,183,721	4,080,699	(475,696)			(703,500)	(1,776,873)	(2,018,692)
Transfer to treasury stock							(36,029,405)
Transfer from grantor trust				36,029,405
Other								(75,013)	21,824
Ending balance, Common stock	1,749,550,587	1,740,529,279	1,733,345,558	463,880,628	272,873,537	208,346,815		36,890,375	38,742,261

Number of shares (or other type of equity) issued during the period as a result of any equity-based compensation plan other than an employee stock ownership plan (ESOP), net of any shares forfeited. Shares issued could result from the issuance of restricted stock, the exercise of stock options, stock issued under employee stock purchase plans, and/or other employee benefit plans.

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- Definition

Number of shares that have been repurchased during the period and have not been retired and are not held in treasury. Some state laws may govern the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

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