Share-Based Compensation (Narrative) (Details) (USD $)	12 Months Ended						12 Months Ended				12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008	Dec. 31, 2011 Minimum Exercise Price Of Options Grant Outstanding [Member]	Dec. 31, 2011 Maximum Exercise Price Of Options Grant Outstanding [Member]	Dec. 31, 2011 Performance Stock Units [Member]	Dec. 31, 2011 Restricted Stock Units (RSUs) [Member]	Dec. 31, 2011 2005 Plan [Member]	May 23, 2008 2005 Plan [Member]	Dec. 31, 2011 2011 Plan Period Two [Member]	Dec. 31, 2011 2011 Plan Period One [Member]	Dec. 31, 2011 Maximum [Member] Performance Stock Units [Member]	Dec. 31, 2011 Minimum [Member] Performance Stock Units [Member]	Dec. 31, 2011 Employee Stock Option [Member]	Dec. 31, 2011 TSR Based PSUs [Member]	Dec. 31, 2011 TSR Based PSUs [Member] Performance Stock Units [Member]	Dec. 31, 2011 Employee Stock Purchase Plan [Member]	Dec. 31, 2010 Employee Stock Purchase Plan [Member]	Dec. 31, 2009 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Additional common stock reserved for issuance										5,000,000
Shares available for grant	4,163,477								4,163,477
Stock options vesting period in years							four	one
Percentage of stock options vested per year	25.00%
Weighted average fair value of stock options granted	$ 11.41	$ 6.68	$ 6.73
Total fair value of shares vested during the year	$ 11,600,000
Performance based shares granted multiplier													200.00%	0.00%
Intrinsic value of share options exercised	18,200,000	5,900,000	100,000
Granted, Share Options	1,859,778	2,114,784	1,571,009
Option grants exercise prices range					$ 1.00	$ 27.21
Option grants outstanding weighted average remaining contractual life, years	6.79
Number of options outstanding	8,485,241	8,553,332	7,590,195	6,301,714					8,686,523
Total unrecognized compensation cost related to unvested share-based payments							3,200,000	70,000							25,800,000
Weighted average period of total unrecognized compensation cost related to unvested share based payments granted, years							2.02	0.14							2.70
Fair value per TSR condition PSU	$ 17.84						$ 18.50	$ 17.30								$ 24.38	$ 24.38
Shares sold to employees under Employee Stock Purchase Plan											12,991	16,991						29,982	48,909	69,806
Employee Stock Purchase Plan, fair value under Period One Plan	$ 152,000
Shares assumed for share-based compensation expense							248,942									16,512
Employee Stock Purchase Plan, number of shares available for issuance																		300,000
Employee Stock Purchase Plan, amended increase in number of shares available for issuance																		600,000
Employee Stock Purchase Plan, remaining number of shares available for issuance																		400,078
Shares sold to employees, price per share											$ 16.47	$ 15.14
Shares sold to employees, closing price per share on the offer termination date											$ 19.38	$ 17.81
Shares sold to employees, closing price per share on the offer termination date percentage											$ 85.00%	$ 85.00%