Capital Stock - Number of Shares Contingently Issuable (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Share Appreciation Program 2008 [Member]
Number of shares contingently issuable
Restricted Shares, nonvested, Beginning Balance, Shares	1,372,000	1,485,000	2,592,000
Granted, Shares			25,000
Forfeited or cancelled, Shares	(1,372,000)	(113,000)	(1,132,000)
Restricted Shares, nonvested, Ending Balance, Shares	0	1,372,000	1,485,000
Weighted-average fair value of grants outstanding		$ 71.28	$ 71.16
Share Appreciation Plan 2005 [Member]
Number of shares contingently issuable
Restricted Shares, nonvested, Beginning Balance, Shares		400,000	1,103,000
Forfeited or cancelled, Shares		(2,000)	(25,000)
Restricted Shares, nonvested, Ending Balance, Shares			400,000
Issued, Shares		(398,000)	(678,000)
Weighted-average fair value of grants outstanding			$ 21.64