Share Capital (Details) - Options (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2004
Summary of stock option plans:
Options exercised during the year	383,000	72,000
Summary of stock options and related activity:
Exercised, shares	(383,000)	(72,000)
Stock Options Member
Summary of stock option plans:
Grants in period (shares)	1,209,000	974,000	1,023,000
Weighted average grant date fair value (per share)	$ 7.65	$ 9.81	$ 9.17
Total intrinsic value of stock options exercised	$ 3,357,000	$ 301,000	$ 667,000
Options exercised during the year	383,000	72,000	91,000
Compensation expense	7,716,000	11,848,000	12,766,000
Estimated tax benefit	26,000	722,000	2,347,000
Summary of stock options and related activity:
Outstanding at beginning of year, shares	12,997,000
Granted, shares	1,209,000
Exercised, shares	(383,000)	(72,000)	(91,000)
Canceled/expired, shares	(1,732,000)
Outstanding at end of year, shares	12,091,000	12,997,000
Options exercisable, shares	9,856,000
Options available for grant, shares	15,695,000
Outstanding at beginning of year, weighted average exercise price	$ 46.30
Granted, weighted average exercise price	$ 20.71
Exercised, weighted average exercise price	$ 14.49
Canceled/expired, weighted average exercise price	$ 89.90
Outstanding at end of year, weighted average exercise price	$ 38.50	$ 46.30
Options exercisable, weighted average exercise price	$ 42.50
Weighted average remaining contractual term, beginning of year	5 years	4 years 10 months 24 days
Weighted average remaining contractual term, end of year	5 years	4 years 10 months 24 days
Weighted average remaining contractual term, options exercisable	4 years 2 months 12 days
Aggregate intrinsic value, beginning of year	20,585,000
Aggregate intrinsic value, end of year	46,803,000	20,585,000
Aggregate intrinsic value, options exercisable	37,435,000
Total unrecognized stock based compensation expense	$ 9,900,000
Period for recognition of unrecognized expense	1 year 3 months 18 days
Number of non-vested options outstanding	2,200,000
Number of stock options issued at an exercise price other than market price				295,000
Exercise price of options issued at above market price				$ 88.00
Market price at time of grant				$ 77.10