Supplemental Disclosures of Cash Flow Information and Non-Cash Financing and Investing Activities - Summary of Significant Non-Cash Investing and Financing Activities (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Significant non-cash investing and financing activities
Other payable issued for purchased customer accounts	$ 9,462	$ 3,339
Estimated acquisition earn-out payables and related charges	71,464	$ 51,717
Notes received on the sale of fixed assets and customer accounts	$ 9,903