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	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Significant non-cash investing and financing activities
Other payable issued for purchased customer accounts	$ 1,883	$ 2,165
Estimated acquisition earn-out payables and related charges	25,085	$ 74,754
Common stock issued for agency acquisition	4,892
Notes payable issued or assumed for purchased customer accounts	$ 1,355