Acquisitions - Schedule of Recognized Identifiable Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Assets acquired:
Goodwill	$ 465,762	$ 458,737
Series of Individually Immaterial Business Acquisitions
Assets acquired:
Cash	671
Accounts receivable	3,320
Other receivables	448
Inventories	3,366
Prepaid and other current assets	146
Property and equipment	2,164
Goodwill	8,404
Intangible assets	4,200
Other assets	50
Total assets acquired	22,769
Liabilities assumed:
Accounts payable	(530)
Accrued expenses and other current liabilities	(348)
Total liabilities assumed	(878)
Total net assets acquired	$ 21,891