Business segment information - Selected Financial Information by Reporting Segment (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Segment Related Capital Expenditure And Depreciation And Amortization On Those Expenditure [Line Items]
Depreciation and amortization	$ 20,261	$ 22,776	$ 22,521
Spine [Member]
Segment Related Capital Expenditure And Depreciation And Amortization On Those Expenditure [Line Items]
Depreciation and amortization	12,152	11,060	9,407
Orthopedics [Member]
Segment Related Capital Expenditure And Depreciation And Amortization On Those Expenditure [Line Items]
Depreciation and amortization	5,604	5,506	6,282
Corporate [Member]
Segment Related Capital Expenditure And Depreciation And Amortization On Those Expenditure [Line Items]
Depreciation and amortization	$ 70	$ 52	$ 126