Business Combinations - Additional Information (Detail) - USD ($) $ in Thousands		3 Months Ended	12 Months Ended
	Apr. 30, 2013	Mar. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Business Acquisition [Line Items]
Acquisition, net of cash acquired			$ 0	$ 0	$ 7,652
Goodwill			61,074	61,369	61,623
Impairment of goodwill			0	0	40,693
Gross profit			640,110	578,443	498,106
Scanners and CAD/CAM Services
Business Acquisition [Line Items]
Impairment of goodwill		$ 40,700
Gross profit			11,923	15,554	13,271
Clear Aligner
Business Acquisition [Line Items]
Gross profit			$ 628,187	$ 562,889	$ 484,835
ICA Holdings Pty Limited [Member]
Business Acquisition [Line Items]
Acquisition, net of cash acquired	$ 8,600
Goodwill	3,600
Assets acquired	7,400
Liabilities assumed	$ 2,400