Acquisitions - Fair Values of Assets Acquired and Liabilities Assumed at Date of Closing - Zhongli (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014	Dec. 15, 2014	Dec. 31, 2013
Business Acquisition [Line Items]
Goodwill	$ 232,240	$ 167,547		$ 134,062
Zhongli [Member]
Business Acquisition [Line Items]
Current assets (including cash of $1,025)			$ 16,223
Property and equipment			1,477
Goodwill			4,752
Intangible - finite life, net			4,262
Intangible - indefinite life			960
Total assets acquired			27,674
Current liabilities assumed			(1,840)
Deferred tax liabilities			(1,739)
Net assets acquired			$ 24,095