CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Cash flows from operating activities:
Net income	$ 485,387	$ 383,163
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization	88,562	80,190
Depreciation	25,457	18,836
Non-cash stock-based compensation	46,659	43,465
Change in estimated acquisition earn-out payables	20,643	4,996
Deferred income taxes	25,417	4,598
Amortization of debt discount and disposal of deferred financing costs	2,081	1,619
Amortization (accretion) of discounts and premiums, investment	119	26
Net (gain)/loss on sales of investments, fixed assets and customer accounts	(2,019)	(720)
Payments on acquisition earn-outs in excess of original estimated payables	(5,747)	(1,199)
Effect of changes in foreign exchange rate changes	475
Changes in operating assets and liabilities, net of effect from acquisitions and divestitures:
Premiums, commissions and fees receivable (increase) decrease	(66,431)	(63,124)
Reinsurance recoverables (increase) decrease	(176,961)	(48,959)
Prepaid reinsurance premiums (increase) decrease	(33,637)	(31,594)
Other assets (increase) decrease	(6,536)	4,071
Premiums payable to insurance companies increase (decrease)	(37,999)	58,986
Premium deposits and credits due customers increase (decrease)	37,486	1,823
Losses and loss adjustment reserve increase (decrease)	176,961	48,959
Unearned premiums increase (decrease)	33,637	31,594
Accounts payable increase (decrease)	45,847	53,041
Accrued expenses and other liabilities increase (decrease)	(796)	(22,458)
Other liabilities increase (decrease)	(30,762)	(27,725)
Net cash provided by operating activities	627,843	539,588
Cash flows from investing activities:
Additions to fixed assets	(34,617)	(55,820)
Payments for businesses acquired, net of cash acquired	(178,007)	(402,358)
Proceeds from sales of fixed assets and customer accounts	9,327	8,622
Purchases of investments	(12,363)	(10,129)
Proceeds from sales of investments	9,280	7,434
Net cash used in investing activities	(206,380)	(452,251)
Cash flows from financing activities:
Payments on acquisition earn-outs	(36,115)	(9,859)
Proceeds from long-term debt		700,000
Payments on long-term debt	(52,500)	(41,250)
Deferred debt issuance costs		(6,788)
Borrowings on revolving credit facility		250,000
Payments on revolving credit facilities		(350,000)
Issuances of common stock for employee stock benefit plans	33,834	29,940
Repurchase shares to fund tax withholdings for non-cash stock-based compensation	(49,594)	(41,126)
Purchase of treasury stock	(82,564)	(7,313)
Cash dividends paid	(78,281)	(72,075)
Net cash (used in) provided by financing activities	(265,220)	451,529
Effect of foreign exchange rate cash changes	(2,267)
Net increase in cash and cash equivalents inclusive of restricted cash	153,976	538,866
Cash and cash equivalents inclusive of restricted cash at beginning of period	1,271,915	962,975
Cash and cash equivalents inclusive of restricted cash at end of period	$ 1,425,891	$ 1,501,841