Capital Stock (Details 3) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Summary of stock options issued under the Stock options plan, the 2007 Plan and Performance Plan in 2010
Outstanding, beginning of year, Shares	5,861
Outstanding, beginning of year, Weighted Average exercise Price	$ 80.30
Granted, Shares	1,336
Granted, Weighted Average Exercise Price	$ 126.61
Exercised, Shares	(878)
Exercised, Weighted Average Exercise Price	$ 63.61
Forfeited or expired, Shares	(227)
Forfeited or expired, Weighted Average Exercise Price	$ 104.74
Outstanding, end of year, Shares	6,092	5,861
Outstanding, end of year, Weighted Average Exercise Price	$ 91.95	$ 80.30
Expected to vest, Shares	2,135
Expected to vest, Weighted Average Exercise Price	$ 109.28
Exercisable, end of year, Shares	3,422
Exercisable, end of year, Weighted Average Exercise Price	$ 77.74
Available for grant, end of year	25,408
Weighted average fair value of options granted during the year	$ 42.20	$ 34.12	$ 29.71