Stock-Based Compensation (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011	Dec. 31, 2010
Stock-based compensation
Number of shares available for grant	2,992,748		2,992,748		3,346,508
Stock option / award activity
Number of shares available for grant	2,992,748		2,992,748		3,346,508
Stock options / awards
Stock-based compensation expense	$ 3,800	$ 2,800	$ 7,200	$ 5,000
Stock options
Stock-based compensation
Number of shares available for grant	2,992,748	3,233,548	2,992,748	3,233,548
Stock option / award activity
Options outstanding at the beginning of the period (in shares)			3,948,874	3,722,656	3,722,656
Granted (in shares)			736,000	781,000
Exercised (in shares)			(53,736)	(44,398)
Forfeited (in shares)			(600,958)	(322,424)
Options outstanding at the end of the period (in shares)	4,030,180	4,136,834	4,030,180	4,136,834	3,948,874	3,722,656
Number of shares available for grant	2,992,748	3,233,548	2,992,748	3,233,548
Total shares reserved at the end of period	7,022,928	7,370,382	7,022,928	7,370,382
Options exercisable at the end of period (in shares)	2,590,876	2,685,545	2,590,876	2,685,545
WEIGHTED-AVERAGE EXERCISE PRICE
Options outstanding at the beginning of the period (in dollars per option)			$ 28.91	$ 33.29	$ 33.29
Granted (in dollars per option)			$ 18.22	$ 16.52
Exercised (in dollars per option)			$ 15.33	$ 11.97
Forfeited (in dollars per option)			$ 35.19	$ 55.57
Options outstanding at the end of the period (in dollars per option)	$ 26.20	$ 28.61	$ 26.20	$ 28.61	$ 28.91	$ 33.29
Options exercisable at the end of period (in dollars per option)	$ 30.54	$ 33.83	$ 30.54	$ 33.83
WEIGHTED-AVERAGE REMAINING CONTRACTUAL LIFE (in years)
Weighted average remaining contractual life, Options outstanding at the end of the period			3 years	2 years 10 months 24 days	2 years 4 months 24 days	2 years 9 months 18 days
Weighted average remaining contractual life, Options exercisable at the end of the period			1 year 10 months 24 days	2 years 2 months 12 days
AGGREGATE INTRINSIC VALUE
Aggregate intrinsic value, Options outstanding at the end of the period	19,230	885	19,230	885
Aggregate intrinsic value, Options exercisable at the end of period	8,883	577	8,883	577
Stock options / awards
Stock-based compensation expense	1,200	1,100	2,300	2,100
Intrinsic values of stock options exercised	8	29	340	284
2004 Non-Employee Director Stock Plan and predecessor plans
Stock-based compensation
Expiration period of stock options from date of grant			10 years
Non-Employee Director Stock Plans
Stock options / awards
Stock-based compensation expense	108	102	189	210
2011 Non-Employee Director Stock Plan (the Director Plan)
Stock-based compensation
Number of shares authorized for issuance to each director			3,000
The maximum period of time that can elapse subsequent to a new director's appointment prior to receipt of an initial award in accordance with the plan			30 days
Number of shares available for grant	158,000		158,000		176,000
Stock option / award activity
Number of shares available for grant	158,000		158,000		176,000
Restricted stock units
Stock options / awards
Stock-based compensation expense	$ 2,500	$ 1,600	$ 4,800	$ 2,700