Income taxes (Details 1) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Tax Disclosure [Abstract]
Computed tax benefit at the federal statutory rate of 35%	$ 19,069	$ 4,879	$ 2,757
State income taxes, net of federal benefit	(57)	(50)	(130)
Non-deductible compensation	(537)	(30)	(532)
Non-deductible expense	(131)	(132)	(156)
Non-deductible goodwill impairment	(15,490)	0	0
Tax on foreign income	(252)	(262)	(154)
Valuation allowance	(4,186)	(6,090)	(3,681)
Other	(18)	105	179
Income tax provision	$ (1,602)	$ (1,580)	$ (1,717)
Effective tax rate	2.90%	11.30%	21.80%

A ratio calculated by dividing the reported amount of income tax expense attributable to continuing operations for the period by GAAP-basis pretax income from continuing operations.

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The sum of foreign current income tax expense or benefit and foreign deferred income tax expense or benefit pertaining to Income or Loss from continuing foreign operations.

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The sum of the current income tax expense or benefit and the deferred income tax expense or benefit pertaining to pretax Income or Loss from continuing operations; income tax expense or benefit may include interest and penalties on tax uncertainties based on the entity's accounting policy.

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The portion of the difference between total income tax expense or benefit as reported in the Income Statement and the expected income tax expense or benefit computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations attributable to changes in the valuation allowance for deferred tax assets in the period.

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The amount of income tax expense or benefit for the period computed by applying the domestic federal statutory tax rates to pretax income from continuing operations.

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The sum of the differences between total income tax expense or benefit as reported in the Income Statement for the period and the expected income tax expense or benefit computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations attributable to nondeductible expenses under enacted tax laws, or differences in the methodologies used to determine expense amounts for financial statements prepared in accordance with generally accepted accounting principles and enacted tax laws.

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The portion of the difference between total income tax expense or benefit as reported in the Income Statement for the period and the expected income tax expense or benefit computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations attributable to nondeductible impairment losses under enacted tax laws.

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The portion of the difference between total income tax expense or benefit as reported in the Income Statement for the period and the expected income tax expense or benefit computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations attributable to differences in the deductibility of incentive stock options and other equity-based compensation costs in accordance with generally accepted accounting principles and enacted tax laws.

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The portion of the difference, between total income tax expense or benefit as reported in the Income Statement for the year/accounting period and the expected income tax expense or benefit computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations, that is attributable to all other items not otherwise listed in the existing taxonomy.

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The portion of the difference, between total income tax expense or benefit as reported in the Income Statement for the period and the expected income tax expense or benefit computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations, that is attributable to state and local income tax expense or benefit.

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