Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
OPERATING ACTIVITIES
Net income	$ 294,156	$ 844,331
Adjustments to reconcile net income to net cash used for operating activities:
Depreciation and amortization	75,899	68,723
Provision for credit losses	(4,032)	(2,407)
Stock-based compensation	37,309	78,346
Deferred income taxes	(35,269)	(76,362)
Excess tax benefit on stock-based compensation	(9,899)	(12,440)
Restructuring charges	21,113	0
Other operating activities	3,740	(24,011)
Changes in operating elements:
Receivables	525,761	66,536
Contract assets	52,810	90,481
Prepaid expenses and other	(7,632)	13,437
Accounts payable and outstanding checks	(122,312)	(109,493)
Accrued compensation	(106,943)	6,701
Accrued transportation expense	(42,481)	(62,278)
Accrued income taxes	3,131	(24,202)
Other accrued liabilities	(2,636)	22,209
Other assets and liabilities	1,900	(2,782)
Net cash provided by operating activities	684,615	876,789
INVESTING ACTIVITIES
Purchases of property and equipment	(25,889)	(50,719)
Purchases and development of software	(42,086)	(49,935)
Proceeds from sale of property and equipment	1,324	63,208
Net cash used for investing activities	(66,651)	(37,446)
FINANCING ACTIVITIES
Proceeds from stock issued for employee benefit plans	46,061	93,415
Stock tendered for payment of withholding taxes	(23,754)	(26,597)
Repurchase of common stock	(63,884)	(1,023,578)
Cash dividends	(218,942)	(216,258)
Proceeds from long-term borrowings	0	200,000
Proceeds from short-term borrowings	2,778,750	3,674,000
Payments on short-term borrowings	(3,169,750)	(3,595,000)
Net cash used for financing activities	(651,519)	(894,018)
Effect of exchange rates on cash and cash equivalents	(6,708)	(15,206)
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect, Disposal Group, Including Discontinued Operations	(40,263)	(69,881)
Less: net increase in cash and cash equivalents within assets held for sale	(2,486)	0
Cash and cash equivalents, beginning of period	217,482	257,413
Cash and cash equivalents, end of period	$ 174,733	$ 187,532