Business Combination - Additional Information (Detail) (USD $)	2 Months Ended	3 Months Ended		9 Months Ended
	Jun. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Apr. 29, 2011
Business Acquisition [Line Items]
Aggregate cash purchase price		$ 187,600,000		$ 187,600,000
Business acquisition, goodwill						135,349,000
Impairment of goodwill		24,665,000	0	24,665,000	0
Contributed gross profit	4,600,000	2,000,000		8,600,000
Contributed net revenues	18,100,000	9,800,000		33,500,000
Scanners and CAD/CAM Services
Business Acquisition [Line Items]
Business acquisition, goodwill		77,300,000		77,300,000
Clear Aligner
Business Acquisition [Line Items]
Business acquisition, goodwill		$ 58,000,000		$ 58,000,000