Goodwill and intangible assets Schedule of Finite-Lived Intangible Assets (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 5,575		$ 5,575		$ 5,575
Gross Carrying Amount	4,370		4,370		4,370
Accumulated Amortization	1,665		1,665		1,229
Net Carrying Amount	2,705		2,705		3,141
Amortization expense	200	200	436	502
Trademarks
Finite-Lived Intangible Assets [Line Items]
Weighted Average Useful Life (years)			6 years 10 months 24 days
Gross Carrying Amount	70		70		70
Accumulated Amortization	23		23		16
Net Carrying Amount	47		47		54
Non-Compete Agreements
Finite-Lived Intangible Assets [Line Items]
Weighted Average Useful Life (years)			2 years
Gross Carrying Amount	70		70		70
Accumulated Amortization	35		35		13
Net Carrying Amount	35		35		57
Customer Relationships
Finite-Lived Intangible Assets [Line Items]
Weighted Average Useful Life (years)			8 years 7 months 6 days
Gross Carrying Amount	2,350		2,350		2,350
Accumulated Amortization	904		904		690
Net Carrying Amount	1,446		1,446		1,660
Developed Technology
Finite-Lived Intangible Assets [Line Items]
Weighted Average Useful Life (years)			6 years
Gross Carrying Amount	1,880		1,880		1,880
Accumulated Amortization	703		703		510
Net Carrying Amount	$ 1,177		$ 1,177		$ 1,370