Property and Equipment (Details 1) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Depreciation and amortization expense relating to:
Total depreciation and amortization expense	$ 4,355	$ 3,270	$ 2,212
Property and equipment [Member]
Depreciation and amortization expense relating to:
Total depreciation and amortization expense	598	510	615
Rental equipment [Member]
Depreciation and amortization expense relating to:
Total depreciation and amortization expense	3,671	2,760	1,597
Service contracts [Member]
Depreciation and amortization expense relating to:
Total depreciation and amortization expense	$ 86