Stock Incentive Plans (Details) (USD $)	1 Months Ended									2 Months Ended					12 Months Ended
	Jul. 31, 2012	Jan. 31, 2012	Dec. 31, 2011	Oct. 31, 2011	Jul. 31, 2011	May 31, 2011	Jan. 31, 2011	Oct. 31, 2010	Feb. 28, 2010	Oct. 31, 2012	May 31, 2012	Apr. 30, 2011	Aug. 31, 2010	Apr. 30, 2010	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Shares available for grant
Shares available for grant, Beginning balance		2,259,999					643,850								2,259,999	643,850	874,269
Shares available for grant, Authorized																2,100,000
Shares available for grant, Granted															(106,395)	(389,774)	(238,826)
Shares available for grant, Exercised
Shares available for grant, Expired																(139,988)
Shares available for grant, Canceled/ forfeited															47,000	45,911	8,407
Shares available for grant, Ending balance			2,259,999												2,200,604	2,259,999	643,850
Number of options outstanding
Number of options outstanding, Beginning balance		2,093,108					1,830,397								2,093,108	1,830,397	2,194,286
Number of options outstanding, Authorized
Number of options, granted	7,000	8,500	143,000	75,400	12,500	51,650	26,000	35,000	7,500	36,800	36,750	73,500	145,655	50,671	89,050	382,050	238,826
Number of options outstanding, Exercised															(17,885)	(73,428)	(594,308)
Number of options outstanding, Expired
Number of options outstanding, Canceled/ forfeited															(47,163)	(45,911)	(8,407)
Number of options outstanding, Ending balance			2,093,108												2,117,110	2,093,108	1,830,397
Weighted - average option exercise price
Weighted - average option exercise price, Beginning balance		$ 13.45					$ 12.98								$ 13.45	$ 12.98	$ 9.48
Weighted - average option exercise price, Authorized
Weighted - average option exercise price, Granted															$ 9.72	$ 16.02	$ 27.54
Weighted - average option exercise price, Exercised															$ 4.01	$ 10.78	$ 5.86
Weighted - average option exercise price, Expired
Weighted - average option exercise price, Canceled/ forfeited															$ 15.13	$ 20.15	$ 16.63
Weighted - average option exercise price, Ending balance			$ 13.45												$ 13.32	$ 13.45	$ 12.98
Number of restricted stock and board shares issued
Number of restricted stock and board shares issued, Beginning balance		42,587					34,863								42,587	34,863	34,863
Number of restricted stock and board shares issued, Authorized
Number of restricted stock and board shares issued, Granted															17,345	7,724
Number of restricted stock and board shares issued, Exercised
Number of restricted stock and board shares issued, Expired
Number of restricted stock and board shares issued, Canceled/ forfeited
Number of restricted stock and board shares issued, Ending balance			42,587												59,932	42,587	34,863