Business Combinations - Summary of Estimated Fair Value of Assets Acquired and Liabilities Assumed (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Business Acquisition [Line Items]
Goodwill	$ 144,244		$ 107,086
Less seller obligations	2,503	$ 1,052
Alpha [Member]
Business Acquisition [Line Items]
Cash	247
Accounts receivable	30,405
Inventories	1,751
Other current assets	6,030
Property and equipment	1,528
Intangibles	57,100
Goodwill	36,452
Other non-current assets	150
Accounts payable and other current liabilities	(16,992)
Fair value of assets acquired and purchase price	116,671
Less fair value of common stock issued	10,859
Less seller obligations	2,002
Cash paid	103,810
Other Acquisition [Member]
Business Acquisition [Line Items]
Accounts receivable	1,096
Inventories	772
Property and equipment	462
Intangibles	1,904
Goodwill	496
Other non-current assets	82
Accounts payable and other current liabilities	(1,001)
Fair value of assets acquired and purchase price	3,811
Less seller obligations	501
Cash paid	3,310
Combined Business Acquisitions [Member]
Business Acquisition [Line Items]
Cash	247
Accounts receivable	31,501	1,518
Inventories	2,523	311
Other current assets	6,030	8
Property and equipment	1,990	789
Intangibles	59,004	5,036
Goodwill	36,948	3,220
Other non-current assets	232	24
Accounts payable and other current liabilities	(17,993)	(1,239)
Fair value of assets acquired and purchase price	120,482	9,667
Less fair value of common stock issued	10,859
Less seller obligations	2,503	870
Cash paid	$ 107,120	$ 8,797