Business segment information - Operating Income (Loss) by GBU (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Product Type Reporting Information [Line Items]
Operating income (loss)	$ 89,010	$ 31,309	$ 66,250
Spine [Member]
Product Type Reporting Information [Line Items]
Operating income (loss)	90,771	46,618	80,688
Orthopedics [Member]
Product Type Reporting Information [Line Items]
Operating income (loss)	15,280	12,368	5,878
Corporate [Member]
Product Type Reporting Information [Line Items]
Operating income (loss)	$ (17,041)	$ (27,677)	$ (20,316)