CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
OPERATING ACTIVITIES
Net income	$ 213,521	$ 71,100	$ 39,985
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	118,864	114,379	108,099
Amortization of intangibles	5,357	4,012	4,367
Pension settlement expense		89	8,505
Share-based compensation expense	11,426	10,478	9,523
Provision for losses on accounts receivable	1,466	4,327	1,223
Change in deferred income taxes	(7,589)	7,715	5,411
Asset impairment			26,514
Gain on sale of property and equipment and lease termination	(8,520)	(2,376)	(5,247)
Gain on sale of subsidiaries	(6,923)
Changes in operating assets and liabilities:
Receivables	(122,782)	(38,129)	13,720
Prepaid expenses	(1,482)	(7,966)	(4,756)
Other assets	354	2,646	(1,365)
Income taxes	13,136	(1,712)	(8,720)
Operating right-of-use assets and lease liabilities, net	623	756	728
Accounts payable, accrued expenses, and other liabilities	106,064	40,670	(27,623)
NET CASH PROVIDED BY OPERATING ACTIVITIES	323,515	205,989	170,364
INVESTING ACTIVITIES
Purchases of property, plant and equipment, net of financings	(58,412)	(43,248)	(90,955)
Proceeds from sale of property and equipment	13,815	13,348	13,490
Business acquisitions, net of cash acquired	(239,380)
Proceeds from sale of subsidiaries	9,013
Purchases of short-term investments	(56,011)	(165,133)	(129,709)
Proceeds from sale of short-term investments	73,182	216,735	120,409
Purchase of long-term investments	(25,350)
Capitalization of internally developed software	(20,061)	(14,241)	(11,476)
NET CASH PROVIDED BY (USED IN) INVESTING ACTIVITIES	(303,204)	7,461	(98,241)
FINANCING ACTIVITIES
Borrowings under credit facilities	50,000	180,000
Borrowings under accounts receivable securitization program		45,000
Proceeds from notes payable	3,523		20,410
Payments on long-term debt	(171,915)	(326,098)	(58,938)
Net change in book overdrafts	(1,957)	6,510	(2,722)
Deferred financing costs	(314)		(562)
Payment of common stock dividends	(8,139)	(8,157)	(8,187)
Purchases of treasury stock	(83,100)	(6,595)	(9,110)
Forward contract for accelerated share repurchase	(25,000)
Payments for tax withheld on share-based compensation	(10,743)	(2,065)	(1,291)
NET CASH USED IN FINANCING ACTIVITIES	(247,645)	(111,405)	(60,400)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	(227,334)	102,045	11,723
Cash and cash equivalents at beginning of period	303,954	201,909	190,186
CASH AND CASH EQUIVALENTS AT END OF PERIOD	76,620	303,954	201,909
NONCASH INVESTING ACTIVITIES
Equipment and other financings	59,700	61,803	70,372
Accruals for equipment received	1,704	1,667	234
Lease liabilities arising from obtaining right-of-use assets	$ 14,671	$ 67,819	$ 32,761