Stock-Based Compensation (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended					12 Months Ended
	Dec. 31, 2011 Common Stock	Dec. 31, 2010 Common Stock	Dec. 31, 2012 A&R 2004 Plan Common Stock	Dec. 31, 2012 2010 Plan	May 31, 2010 2010 Plan	Dec. 31, 2010 IPO in 2010 A&R 2004 Plan	Dec. 31, 2010 Subsequent to IPO A&R 2004 Plan	Dec. 31, 2012 Stock Options	Dec. 31, 2011 Stock Options	Dec. 31, 2010 Stock Options	Dec. 31, 2012 Stock Options A&R 2004 Plan	Dec. 31, 2011 Stock Options A&R 2004 Plan	Dec. 31, 2010 Stock Options A&R 2004 Plan	Dec. 31, 2012 Restricted Stock	Dec. 31, 2011 Restricted Stock	Dec. 31, 2010 Restricted Stock	Dec. 31, 2012 Unrestricted Stock	Dec. 31, 2011 Unrestricted Stock	Dec. 31, 2010 Unrestricted Stock	Dec. 31, 2012 Restricted Stock Units	Dec. 31, 2011 Restricted Stock Units
Stock-based compensation
Number of shares of common stock reserved for issuance				1,689,912							37,240
Expiration period											10 years
Maximum number of shares of common stock that may be issued					2,130,000
Options
Outstanding at the beginning of the year (in shares)											37,240	356,623	819,185
Exercised (in shares)	(319,383)	(95,000)	95,000			(288,001)	(174,571)					(319,383)	(462,562)
Outstanding at the end of the year (in shares)											37,240	37,240	356,623
Exercisable at the end of the year (in shares)											37,240	37,240	309,113
Weighted average price
Outstanding at the beginning of the year (in dollars per share)											$ 4.21	$ 4.21	$ 4.21
Exercised (in dollars per share)												$ 4.21	$ 4.21
Outstanding at the end of the year (in dollars per share)											$ 4.21	$ 4.21	$ 4.21
Exercisable at the end of the year (in dollars per share)											$ 4.21	$ 4.21	$ 4.21
Stock options, additional disclosure
Number of stock options exercised by stockholders utilizing a broker assisted cashless exercise (in shares)												184,236
Compensation expenses recognized										$ 2,975				$ 1,092	$ 848	$ 419	$ 756	$ 1,024	$ 635
Weighted-average remaining contractual life of stock awards								3 years 8 months 12 days	4 years 8 months 12 days	4 years
Weighted-average remaining contractual life of exercisable stock awards								3 years 8 months 12 days	4 years 8 months 12 days	3 years 7 months 6 days
Aggregate intrinsic value of stock awards								379	388
Aggregate intrinsic value of exercisable stock awards								379	388
Aggregate intrinsic value of stock awards exercised									3,200	2,885
Shareholders' notes receivable										482
Shares
Unvested at the beginning of the period (in shares)														235,667,000	242,088,000					18,893,000
Granted (in shares)														42,077,000	43,690,000	242,088,000	58,441,000	68,224,000	44,350,000	14,367,000	20,612,000
Vested (in shares)														(68,921,000)	(50,111,000)					(7,214,000)	1,719,000
Unvested at the end of the period (in shares)														208,823,000	235,667,000	242,088,000				26,046,000	18,893,000
Expected to vest in the future, at the end of the period (in shares)														201,305,000						26,046,000
Weighted Average Grant Date Fair Value
Unvested at the beginning of the period (in dollars per share)														$ 12.27	$ 11.68					$ 15.20
Granted (in dollars per share)														$ 14.57	$ 14.99	$ 11.68	$ 12.94	$ 15.01	$ 14.32	$ 14.35	$ 15.21
Vested (in dollars per share)														$ 12.61	$ 11.77					$ 15.21	$ 15.25
Unvested at the end of the period (in dollars per share)														$ 12.63	$ 12.27	$ 11.68				$ 14.73	$ 15.20
Expected to vest in the future, at the end of the period (in dollars per share)														$ 12.63						$ 14.73
Weighted Average Remaining Contractual Term
Unvested at the beginning of the period														1 year 11 months 8 days	4 years 4 days	4 years 4 days				8 months 19 days	2 years
Granted														2 years	2 years	4 years 4 days				1 year 2 months 12 days
Unvested at the end of the period														1 year 11 months 8 days	4 years 4 days	4 years 4 days				8 months 19 days	2 years
Expected to vest in future, at the end of the period														1 year 11 months 8 days						8 months 19 days
Recognized and unrecognized compensation expense with weighted average recognition period
Unrecognized compensation expense calculated under the fair value method for shares expected to vest														$ 1,685	$ 2,154
Number of shares issued upon exercise of units other than options																				1
Maximum period following a termination of service in which the share-based award will be settled																				2 months 15 days