Capital Stock - Restricted Stock (Detail) (Restricted Stock [Member], USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted Shares, nonvested, Beginning Balance, Shares	2,115,000
Granted, Shares	1,220,000	887,851	1,143,989
Vested, Shares	(1,053,000)
Forfeited or cancelled, Shares	(118,000)
Restricted Shares, nonvested, Ending Balance, Shares	2,164,000	2,115,000
Non-vested at January 1, 2012, Weighted Average Grant Date Fair Value	$ 109.63
Granted, Weighted Average Grant-Date Fair Value	$ 85.67	$ 124.16	$ 103.88
Vested, Weighted Average Grant-Date Fair Value	$ 107.76
Forfeited, Weighted Average Grant-Date Fair Value	$ 102.82
Non-vested at December 31, 2012, Weighted Average Grant Date Fair Value	$ 97.34	$ 109.63