Intangible Assets (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Summary of intangible assets, net
Gross Amount	$ 65,705,000	$ 64,529,000
Accumulated Amortization	(50,864,000)	(46,813,000)
Net	14,841,000	17,716,000
Amortization expenses	3,900,000	4,500,000	7,400,000
Customer Relationships [Member]
Summary of intangible assets, net
Gross Amount	42,397,000	42,194,000
Accumulated Amortization	(28,909,000)	(25,529,000)
Net	13,488,000	16,665,000
Intellectual Property Rights [Member]
Summary of intangible assets, net
Gross Amount	4,300,000	3,350,000
Accumulated Amortization	(2,947,000)	(2,299,000)
Net	1,353,000	1,051,000
Proprietary technology [Member]
Summary of intangible assets, net
Gross Amount	19,008,000	18,985,000
Accumulated Amortization	(19,008,000)	(18,985,000)
Net	$ 0	$ 0