Business Combinations - Purchase Price Allocation for Current Year Acquisitions and Adjustments Made for Prior Year Acquisitions (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Jun. 30, 2020	Jun. 30, 2021
Business Combination Separately Recognized Transactions [Line Items]
Cash paid			$ 162,752
Common stock issued	$ 4,892	$ 10,000	4,892
Other payable			1,883
Recorded earn-out payable			25,085
Net assets acquired			194,612
Maximum potential earn- out payable			46,325
O'Leary Insurances (O'Leary)
Business Combination Separately Recognized Transactions [Line Items]
Net assets acquired			$ 137,648
O'Leary Insurances (O'Leary) | Retail
Business Combination Separately Recognized Transactions [Line Items]
Effective date of acquisition			Jan. 01, 2021
Cash paid			$ 117,408
Common stock issued			4,892
Recorded earn-out payable			15,348
Net assets acquired			137,648
Maximum potential earn- out payable			30,575
Piper Jordan LLC (Piper)
Business Combination Separately Recognized Transactions [Line Items]
Net assets acquired			$ 54,679
Piper Jordan LLC (Piper) | Retail
Business Combination Separately Recognized Transactions [Line Items]
Effective date of acquisition			May 01, 2021
Cash paid			$ 43,428
Other payable			1,397
Recorded earn-out payable			9,854
Net assets acquired			54,679
Maximum potential earn- out payable			15,000
Other Acquisitions
Business Combination Separately Recognized Transactions [Line Items]
Net assets acquired			2,285
Other Acquisitions | Various
Business Combination Separately Recognized Transactions [Line Items]
Cash paid			1,916
Other payable			486
Recorded earn-out payable			(117)
Net assets acquired			2,285
Maximum potential earn- out payable			$ 750