Share-Based Compensation (Narrative) (Details) (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					6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011 Stock Options [Member]	Jun. 30, 2010 Stock Options [Member]	Jun. 30, 2011 Stock Options [Member]	Jun. 30, 2010 Stock Options [Member]	Jun. 30, 2011 Restricted Stock [Member]	Jun. 30, 2010 Restricted Stock [Member]	Jun. 30, 2011 Non-Vested Stock Option Awards [Member]	Dec. 31, 2010 Non-Vested Stock Option Awards [Member]	Jun. 30, 2011 Unvested Restricted Stock and RSUs [Member]	Dec. 31, 2010 Unvested Restricted Stock and RSUs [Member]	Jun. 30, 2011 Unvested Restricted Stock Awards [Member]	Dec. 31, 2010 Unvested Restricted Stock Awards [Member]	Jun. 30, 2011 2001 Stock Option Plan [Member]	Jun. 30, 2011 2004 Incentive Plan [Member]	Jun. 30, 2010 2004 Incentive Plan [Member]	Jun. 30, 2011 2004 Incentive Plan [Member]	Jun. 30, 2010 2004 Incentive Plan [Member]	Jun. 30, 2011 Stock Options That Contain Performance And Market-Based Conditions [Member]	Jun. 30, 2011 Restricted Stock Awards That Contain Performance Or Market Conditions [Member]	Jun. 30, 2010 Restricted Stock Awards That Contain Performance Or Market Conditions [Member]	Jun. 30, 2011 Restricted Stock Awards That Contain Performance Or Market Conditions Awarded In 2009 and 2008 [Member]	Jun. 30, 2011 Employee Stock Purchase Plan [Member]	Jun. 30, 2010 Employee Stock Purchase Plan [Member]	Jun. 30, 2011 Stock Options For Executive Officer [Member]	Jun. 30, 2011 Stock Options For Executive Officer [Member]	Apr. 29, 2012 Stock Options For Executive Officer [Member]	Apr. 29, 2012 Stock Options For Executive Officer Exercisable Each Three Month Period Until 2015 [Member]	Jan. 31, 2015 Performance Or Market Condition Options For CEO [Member]	Apr. 29, 2011 Performance Or Market Condition Options For Vice President [Member]	Jun. 30, 2011 Stock Options For Employees [Member]
Shares authorized to purchase upon grant of options																	7,750,000															250,000	50,000
Minimum vesting period									one
Maximum vesting period									four
Income tax benefit recognized for share-based compensation				$ 0
Vested period for directors																													ten-year term
Shares vested and exercisable																														12,500	3,125
Shares remain available for future grant																		7,264,000		7,264,000
Stock compensation expense			2,136,000	1,434,000														1,700,000	1,000,000	3,300,000	2,300,000	300,000	187,000	50,000
Exercise of stock options and the vesting of restricted stock, income tax deduction	1,100,000		1,300,000
Term of options granted from grant date, years			10
Employee options to purchase shares of common stock			1,487,000																									50,000						1,500,000
Common stock issued upon exercise of outstanding stock options			33,000	188,000
Common stock issued upon exercise of outstanding stock options, proceeds			200,000	1,200,000
Stock option compensation cost charged against income	700,000	500,000					1,600,000	1,300,000	1,200,000	1,100,000																200,000	200,000
Unrecognized compensation cost	5,700,000		5,700,000						6,900,000
Unrecognized compensation, expected to be recognized over a weighted-average period of approximately, years			2.8
Weighted-average grant date per share fair value for options granted	$ 5.01		$ 5.21		$ 6.57	$ 8.28	$ 6.27	$ 8.87														$ 5.21
Total intrinsic value of options exercised							100,000
Closing price of common stock							$ 7.49	$ 12.60
Options remain unvested									917,000		400,000	15,000	917,000	315,000	317,000	39,000						400,000			317,000
Additional compensation expense if the performance targets are met or expected to be attained																						2,700,000			3,100,000
Shares of restricted stock issued									751,000
Total aggregate fair market value of restricted stock issued									6,600,000
Deferred restricted stock compensation cost charged against income	700,000	500,000					1,600,000	1,300,000	1,200,000	1,100,000																200,000	200,000
Weighted-average grant date fair value for restricted stock awards granted									$ 8.74	$ 11.65	$ 5.21	$ 8.43	$ 9.17	$ 11.56	$ 9.82	$ 19.37
Total grant date fair value of restricted shares vested									$ 1,400,000	$ 1,500,000
Rights purchase price, percentage of fair value of rights granted or exercised, not less than																										85.00%