Quarterly Data (unaudited) (Parenthetical) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended													12 Months Ended
	Dec. 31, 2016		Sep. 30, 2016	[2]	Jun. 30, 2016		Mar. 31, 2016		Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Quarterly Financial Information [Line Items]
Loss on repurchases of convertible notes														$ 19,085
Litigation accrual adjustment														43,310	$ 41,826	$ (30,000)
Revenue	$ 271,109	[1],[2]	$ 239,649		$ 236,210	[2],[3]	$ 215,104	[1],[2],[4]	$ 215,282	$ 200,538	$ 202,910	$ 192,383	[5]	962,072	811,113	$ 762,415
OIG [Member]
Quarterly Financial Information [Line Items]
Litigation accrual adjustment												(13,800)
Organization established by former Ellipse Technologies stockholders[Member]
Quarterly Financial Information [Line Items]
Revenue														4,800
Medtronic Litigation [Member]
Quarterly Financial Information [Line Items]
Litigation accrual adjustment					$ 43,300							$ 56,400		$ 43,300	$ 56,400
Convertible Notes due 2017 [Member]
Quarterly Financial Information [Line Items]
Loss on repurchases of convertible notes	$ 1,700						17,400
Accounting Standards Update 2016-09 [Member]
Quarterly Financial Information [Line Items]
Adjustment of provision for income taxes							$ 5,500
Effect of change in net loss per share							$ 0.11

[1] Consolidated financial results include losses from repurchases of Senior Convertible Notes due 2017 of $17.4 million and $1.7 million in the first and fourth quarters of fiscal year 2016, respectively.

[2] The unaudited quarterly financial data set forth for the year ended December 31, 2016 includes the operations and results of Ellipse Technologies, BNN Holdings and the Company’s other acquisitions from their respective dates of acquisition. See Note 5 to the Consolidated Financial Statements included in this Annual Report for further discussion.

[3] Consolidated financial results include a litigation liability gain of $43.3 million in connection with the settlement of all outstanding litigation matters with Medtronic.

[4] The Company elected to early adopt ASU 2016-09 in the second quarter of 2016. As a result, the Company recorded a retrospective adjustment to the previously reported first quarter 2016 provision for income taxes of approximately $5.5 million for the recognition of excess tax benefits in the provision for income taxes rather than additional paid-in capital and a decrease in net loss per share of $0.11 for the three months ended March 31, 2016. See Note 1 to the Consolidated Financial Statements included in this Annual Report for further discussion.

[5] Consolidated financial results include a purchase order for $4.8 million from an organization established by certain former stockholders of Ellipse Technologies. See Note 4 to the Consolidated Financial Statements included in this Annual Report for further discussion on the purchase order.