Stock Based Compensation and Other Benefit Plans (Details ) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 Y	Dec. 31, 2010	Dec. 31, 2009
Summary of stock option activity
Outstanding at beginning of period, Shares	3,901,232
Outstanding at beginning of period, Weighted Average Exercise Price	$ 5.44
Granted, Shares	725,643
Granted, Weighted-Average Exercise Price	$ 9.13	$ 5.61	$ 3.31
Exercised, Shares	671,000	677,000	18,000
Exercised, Weighted Average Exercise Price	$ 5.34
Expired or cancelled, Shares	(333,991)
Expired or cancelled, Weighted Average Exercise Price	$ 5.23
Outstanding at end of period, Shares	3,621,013	3,901,232
Outstanding at end of period, Weighted Average Exercise Price	$ 6.21	$ 5.44
Outstanding, Weighted Average Remaining Contractual Life	6.11
Outstanding, Intrinsic Value	$ 11,908,247
Vested or expected to vest at end of period, Shares	3,554,364
Vested or expected to vest at end of period, Weighted-Average Exercise Price	$ 6.19
Vested or expected to vest at end of period, Weighted Average Remaining Contractual Life	6.07
Vested or expected to vest at end of period, Intrinsic Value	11,762,252
Options exercisable at end of period, Shares	2,079,337
Exercisable, Weighted Average Exercise Price	$ 6.54
Exercisable, Weighted Average Remaining Contractual Life	4.62
Exercisable, Intrinsic Value	$ 6,162,396