Goodwill and Acquired Intangible Assets Impairment of goodwill (Details) (USD $)	1 Months Ended	3 Months Ended			6 Months Ended
	Mar. 31, 2013	Jun. 30, 2013	Mar. 31, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Goodwill [Line Items]
Impairment of goodwill		$ 0	$ 40,700,000	$ 0	$ 40,693,000	$ 0
Goodwill		61,713,000			61,713,000		99,236,000
Asset Impairment Charges	26,300,000	0	26,300,000	0	26,320,000	0
Scanners and CAD/CAM Services
Goodwill [Line Items]
Impairment of goodwill					40,693,000
Goodwill		0			0		40,693,000
Asset Impairment Charges	19,300,000
Property, Plant, Equipment [Member]
Goodwill [Line Items]
Impairment of fixed assets	$ 7,000,000