Consolidated Statements of Changes in Shareholders Equity (USD $) In Thousands, except Share data	Total	Common Shares [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Balance, Amount at Dec. 31, 2009 (Previously Reported [Member])	$ 240,269	$ 1,714	$ 177,246	$ 54,119	$ 7,190
Balance, Shares at Dec. 31, 2009 (Previously Reported [Member])		17,141,710
Cumulative effect of adjustment on opening balance (Adjustments [Member])	(7,649)			(8,296)	647
Net income (loss)	44,296			44,296
Net income (loss) at Jan. 01, 2010 (Previously Reported [Member])	44,208
Net income (loss) (Adjustments [Member])	88
Unrealized gain (loss) on derivative instrument net of taxes	(90)				(90)
Translation adjustment	(1,317)				(1,317)
Translation adjustment at Jan. 01, 2010 (Previously Reported [Member])	(1,710)
Translation adjustment (Adjustments [Member])	393
Tax benefit on exercise of stock options	2,417		2,417
Share-based compensation expense	8,138		8,138
Common shares issued	7,854	58	7,796
Common shares issued, Shares		584,935
Balance, Amount (Restated) at Dec. 31, 2010	293,918	1,772	195,597	90,119	6,430
Balance, Shares (Restated) at Dec. 31, 2010		17,726,645
Net income (loss)	(18,110)			(18,110)
Net income (loss) at Jan. 01, 2011 (Previously Reported [Member])	(1,073)
Net income (loss) (Adjustments [Member])	(17,037)
Unrealized gain (loss) on derivative instrument net of taxes	(437)				(437)
Translation adjustment	(2,279)				(2,279)
Translation adjustment at Jan. 01, 2011 (Previously Reported [Member])	(3,192)
Translation adjustment (Adjustments [Member])	913
Purchase of minority interest	(517)		(517)
Tax benefit on exercise of stock options	1,737		1,737
Reclassification for tax benefit on exercise of stock options	(8,999)		(8,999)
Share-based compensation expense	6,648		6,648
Common shares issued	20,113	74	20,039
Common shares issued, Shares		738,799
Balance, Amount (Restated) at Dec. 31, 2011	292,074	1,846	214,505	72,009	3,714
Balance, Shares (Restated) at Dec. 31, 2011 (Previously Reported [Member])	18,465,444
Balance, Shares (Restated) at Dec. 31, 2011	18,465,444	18,465,444
Net income (loss)	42,838			42,838
Net income (loss) at Jan. 01, 2012 (Previously Reported [Member])	51,295
Net income (loss) (Adjustments [Member])	(8,457)
Unrealized gain (loss) on derivative instrument net of taxes	263				263
Translation adjustment	768				768
Translation adjustment at Jan. 01, 2012 (Previously Reported [Member])	480
Translation adjustment (Adjustments [Member])	288
Share-based compensation expense	6,303		6,303
Common shares issued	25,586	88	25,498
Common shares issued, Shares		873,885
Balance, Amount (Restated) at Dec. 31, 2012	$ 367,832	$ 1,934	$ 246,306	$ 114,847	$ 4,745
Balance, Shares (Restated) at Dec. 31, 2012 (Previously Reported [Member])	19,339,329
Balance, Shares (Restated) at Dec. 31, 2012	19,339,329	19,339,329