Stock Compensation Plans (Narrative) (Details) (USD $)	12 Months Ended				12 Months Ended
	Dec. 31, 2011 years	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 2008 Equity Incentive Plan [Member]	Dec. 31, 2011 Employee Stock Option Plan [Member]	Dec. 31, 2010 Employee Stock Option Plan [Member]	Dec. 31, 2009 Employee Stock Option Plan [Member]	Dec. 31, 2005 Non-Employee Directors' Stock Option Plan [Member]	Dec. 31, 2011 Performance Stock Awards [Member]	Dec. 31, 2010 Performance Stock Awards [Member]	Dec. 31, 2009 Performance Stock Awards [Member]	Dec. 31, 2011 Restricted Stock Awards [Member]	Dec. 31, 2010 Restricted Stock Awards [Member]	Dec. 31, 2009 Restricted Stock Awards [Member]	Dec. 31, 2011 TSR Performance Stock Awards [Member]	Dec. 31, 2011 ROC Performance Stock Awards [Member]	Dec. 31, 2011 Minimum [Member] 2008 Equity Incentive Plan [Member]	Dec. 31, 2011 Minimum [Member] Non-Employee Directors' Stock Option Plan [Member]	Dec. 31, 2011 Minimum [Member] Performance Stock Awards [Member]	Dec. 31, 2011 Minimum [Member] ROC Performance Stock Awards [Member]	Dec. 31, 2011 Maximum [Member] 2008 Equity Incentive Plan [Member]	Dec. 31, 2011 Maximum [Member] Non-Employee Directors' Stock Option Plan [Member]	Dec. 31, 2011 Maximum [Member] Performance Stock Awards [Member]	Dec. 31, 2011 Maximum [Member] ROC Performance Stock Awards [Member]	Dec. 31, 2011 Before Applying Simplified Method [Member] 2011 Grant Of Stock Options [Member] years	Dec. 31, 2011 After Applying Simplified Method [Member] 2011 Grant Of Stock Options [Member] years	Dec. 31, 2011 Incentive Stock Options [Member] 2008 Equity Incentive Plan [Member]	Dec. 31, 2011 Incentive Stock Options [Member] Minimum [Member] Employee Stock Option Plan [Member]	Dec. 31, 2011 Incentive Stock Options [Member] Maximum [Member] Employee Stock Option Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum number of shares available for grants				2,000,000	8,238,640																						1,500,000
Employee percentage used to determine exercise price																											10.00%
Minimum option price of fair market value to exercise awards					100.00%																						110.00%
Exercise period of options from the date of grant																	seven	6 months			ten	10 years						6 months	10 years
Expected lives of options																									10	7
Value of annual grant per director on the date of grant								$ 25,000
Weighted-average grant date fair value per share of options granted					$ 5.47	$ 6.90	$ 6.45
Weighted-average grant date fair value amount of options granted					1,000,000	500,000	600,000
Total weighted-average grant date fair value amount of options granted									500,000	700,000	800,000	1,600,000	1,400,000	1,600,000
Total weighted-average grant date fair value of options vested, per share	$ 6.79	$ 6.60	$ 5.08
Total grant date fair value options vested, value	500,000	500,000	400,000
Total intrinsic value of stock options exercised	2,700,000	1,800,000	800,000
Total amount of cash received from the exercise of options	2,100,000	2,000,000	1,000,000
Performance period of the awards (in years)	three														three	three
Percentage of target award															52.00%				0.00%	0.00%			200.00%	200.00%
Common stock issued under the target award	8,528
Weighted-average grant date fair value per share of awards granted									$ 14.51	$ 25.45	$ 26.83	$ 14.88	$ 16.21	$ 15.08
Weighted-average grant date fair value amount of awards granted									700,000	500,000	700,000	1,400,000	1,900,000	1,800,000
Total fair value of awards vested									500,000	700,000	800,000	1,600,000	1,400,000	1,600,000
Stock-based compensation expense	2,577,000	2,463,000	2,398,000
Income tax benefit related to stock-based compensation	900,000	700,000	700,000
Total future compensation cost related to nonvested awards	$ 2,800,000
Weighted-average period over which future compensation cost is expected to be recognized (in years)	1.6