Equity (Detail) (USD $)	1 Months Ended	9 Months Ended	12 Months Ended
	Jan. 31, 2012	Sep. 30, 2012	Dec. 31, 2011	Mar. 28, 2012	Nov. 30, 2011
Equity [Line Items]
Dividends per share				$ 13.60
Common dividends declared ($13.60 per share)		$ 417,606,000
Dividends payable date		Apr. 20, 2012
Dividend payable record date		Apr. 10, 2012
Equitable adjustment to stock options outstanding		19,058
Equitable adjustment to restricted stock units outstanding		6,875
Additional payout to restricted stock holders who elected cash dividend Distribution		2,500,000
Special distribution declared		$ 29.00
Voting common stock repurchased, authorized shares					800,000
Voting common stock repurchased, shares		18,000	136,494
Voting common stock repurchased		(1,192,000)	(8,400,000)
Treasury stock average price per share		$ 66.22	$ 61.54
Cost of purchase settled	500,000	1,664,000
Treasury stock, shares		154,494	136,494
Cost of shares held		$ 9,592,000	$ 8,400,000
Average cost of shares held		$ 62.09