Capital Stock (Details Textual) (USD $)	3 Months Ended		6 Months Ended				3 Months Ended		6 Months Ended				3 Months Ended		6 Months Ended			3 Months Ended	6 Months Ended	12 Months Ended		3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011 Maximum [Member] Stock Appreciation Rights [Member]	Jun. 30, 2011 Minimum [Member] Stock Appreciation Rights [Member]	Jun. 30, 2011 Stock Option Plan [Member]	Jun. 30, 2010 Stock Option Plan [Member]	Jun. 30, 2011 Stock Option Plan [Member]	Jun. 30, 2010 Stock Option Plan [Member]	Dec. 31, 2010 Stock Option Plan [Member]	Dec. 31, 2009 Stock Option Plan [Member]	Jun. 30, 2011 Options to Non-Employees [Member]	Jun. 30, 2010 Options to Non-Employees [Member]	Jun. 30, 2011 Options to Non-Employees [Member]	Jun. 30, 2010 Options to Non-Employees [Member]	Dec. 31, 2010 Options to Non-Employees [Member]	Jun. 30, 2010 Restricted Common Shares [Member]	Jun. 30, 2010 Restricted Common Shares [Member]	Dec. 31, 2010 Restricted Common Shares [Member]	Jul. 12, 2000 Restricted Common Shares [Member]	Jun. 30, 2011 Stock Appreciation Rights [Member]	Jun. 30, 2010 Stock Appreciation Rights [Member]	Jun. 30, 2011 Stock Appreciation Rights [Member]	Jun. 30, 2010 Stock Appreciation Rights [Member]	Dec. 31, 2007 Stock Appreciation Rights [Member]	Dec. 31, 2010 Stock Appreciation Rights [Member]
Capital Stock (Textuals) [Abstract]
Share-based compensation costs recorded	$ 4,700,000	$ (3,700,000)	$ 8,700,000	$ 5,600,000			$ 2,800,000	$ 1,100,000	$ 4,800,000	$ 1,700,000			$ 500,000		$ 700,000			$ (500,000)	$ 200,000			$ 1,400,000	$ (4,400,000)	$ 3,200,000	$ 3,600,000
Share-based compensation costs charged for the period														less than 0.1		less than 0.1
Reserved common shares for future issuance							12,913,511		12,913,511		12,829,115
Options outstanding							7,409,881	6,360,976	7,409,881	6,360,976	6,743,272	6,173,795	107,501	91,885	107,501	91,885
Options outstanding, weighted average exercise price							$ 13.87	$ 8.38	$ 13.87	$ 8.38	$ 10.79	$ 6.52	$ 14.31	$ 13.43	$ 14.31	$ 13.43
Options fully vested or expected to vest, weighted average exercise price							$ 13.47		$ 13.47
Stock based awards vesting period					5 years	0 years			1 to 5 years
Stock based awards expiration period or remaining contractual life									10 years or less						6 Years									P6.51Y
Options common shares were vested and exercisable							3,121,874		3,121,874
Options fully vested, expected							6,790,608		6,790,608
Options fully vested or expected to vest, weighted average remaining contractual life									4.8
Options fully vested or expected to vest, aggregate intrinsic value							129,300,000		129,300,000				200,000		200,000
Options fully vested or expected to vest, aggregate intrinsic value														less than 0.1		less than 0.1
Weighted average remaining contractual life of exercisable option									3.2
Options exercisable intrinsic value							77,800,000		77,800,000
Intrinsic value of options exercised							6,300,000	2,600,000	8,700,000	8,300,000
Options granted									1,107,342	1,047,689			0	50,000	103,944	61,217
Options granted to purchase the company's common stock, average exercise price													$ 0	$ 18.98	$ 27.64	$ 18.12
Common share options subject to vesting based on performance commitment													20,000		20,000
Options exercisable							3,121,874	3,093,225	3,121,874	3,093,225			9,500	11,217	9,500	11,217
Options exercisable, weighted average exercise price							$ 7.61	$ 6.05	$ 7.61	$ 6.05			$ 14.40	$ 14.31	$ 14.40	$ 14.31
Weighted average fair value of options granted							$ 7.72	$ 8.00	$ 9.6	$ 7.27			$ 0	$ 8.08	$ 13.75	$ 8.15										$ 6.20
Amount of stock options or rights included in accrued liabilities													less than 0.1		less than 0.1
Amount of stock options or rights included in accrued liabilities																	1,500,000					3,100,000		3,100,000			23,700,000
Restricted common shares required to be issued under employment agreements																					160,000
Cash paid in settlement																				4,200,000		13,000,000	3,300,000	23,700,000	5,400,000
Share-based compensation arrangement by share-based payment award, equity instruments other than options, nonvested, number																						133,000		133,000
Number of rights settled in cash																						0	210,000
Stock appreciation rights granted																						472,000	270,000	999,500	480,000	2,280,000
Average exercise price of cash settled rights																						$ 6.86	$ 5.74	$ 6.86	$ 5.13
Share based compensation arrangement by share based payment award equity instruments other than options exercisable																						100,000		100,000
Stock appreciation rights forfeited, cancelled or expired																						0	0	0	0
Share-based compensation arrangement by share-based payment award, equity instruments other than options, nonvested, weighted average grant date fair value																						$ 25.31		$ 25.31			$ 21.21