Shareholders' Equity (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	May 25, 2011	May 23, 2008
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted, shares	1,105,039
Common stock, shares authorized	250,000,000	250,000,000
Outstanding awards, shares	4,316,869	3,783,429
Vesting period, minimum, years	four
Options expiration period, in years	7
Compensation expense	11,296,000	8,955,000	7,875,000
Compensation expense recognition period, in months	3
Common stock, shares outstanding	59,717,000	60,191,000
Anti-dilutive common stock shares available for purchase for employees and directors	4,316,869	3,616,015
Aggregate total of share repurchase authorization approved by Board of Directors	10,000,000	75,000,000
Repurchase of outstanding common stock	936,533	1,835,865
Average price per share, share repurchase agreement	10.68	10.89
Amount of outstanding common stock, repurchased	(10,019,000)	(20,037,000)
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cash received from option exercises	200,000	600,000	600,000
Tax benefit from option exercises	100,000	600,000	700,000
Total unrecognized compensation cost	8,100,000
Weighted-average period of recognition, years	3.60
Stock Options [Member] | Employee Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted, shares	962,175
Stock options granted, average fair value	3.84	4.68	5.05
Stock Options [Member] | Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted, shares	142,864
Stock options granted, average fair value	4.48	5.09	5.48
Stock Options [Member] | 2008 Omnibus Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted, shares	2,903,659
Common stock, shares authorized				5,600,000
Available for grant, shares	3,900,000				8,414,363
Reduction in the number of stock options and restricted deferred stock units that would be granted, percentage		75.00%	25.00%
Stock Options [Member] | Prior Plans [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted, shares	1,413,210
Vesting period, minimum, years	five
Options expiration period, in years	10
Stock Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation cost	7,100,000
Weighted-average period of recognition, years	1.90
Shared Performance Stock Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation cost	300,000
Performance period, years	3
Performance target, minimum, percentage	0.00%
Performance target, maximum, percentage	200.00%
Vesting period, in months	36
2008 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares authorized	1,500,000
Common stock purchase limit to authorize payroll deduction, maximum, value	25,000
Fair market value of a common stock, purchased from accumulated payroll deductions, percentage	85.00%
Discount given to participants for the purchase of shares under employee stock purchase plan, percentage	15.00%
Compensation expense	300,000	200,000	500,000
Capital Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares authorized	250,000,000	250,000,000
Common stock, par or stated value per share	0.01	0.01
Preferred stock, shares authorized	50,000,000	50,000,000
Preferred stock, par or stated value per share	0.01	0.01
Common stock, shares outstanding	59,717,242	60,190,605
Maximum [Member] | Stock Options [Member] | 2008 Omnibus Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Available for grant, shares					4,764,363
Options Granted Prior To 2011 [Member] | Stock Options [Member] | 2008 Omnibus Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period, years	four
Options expiration period, in years	10
Options Granted In 2011 [Member] | Stock Options [Member] | 2008 Omnibus Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period, years	three
Options expiration period, in years	7