CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
OPERATING ACTIVITIES
Net income	$ 71,100	$ 39,985	$ 67,262
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	114,379	108,099	104,114
Amortization of intangibles	4,012	4,367	4,521
Pension settlement expense, including termination expense	89	8,505	12,925
Share-based compensation expense	10,478	9,523	8,413
Provision for losses on accounts receivable	4,327	1,223	2,336
Change in deferred income taxes	7,715	5,411	1,872
Asset impairment		26,514
Gain on sale of property and equipment and lease termination	(2,376)	(5,247)	(59)
Gain on sale of subsidiaries			(1,945)
Changes in operating assets and liabilities:
Receivables	(38,129)	13,720	(23,554)
Prepaid expenses	(7,966)	(4,756)	(2,988)
Other assets	2,646	(1,365)	(4,341)
Income taxes	(1,712)	(8,720)	12,169
Operating right-of-use assets and lease liabilities, net	756	728
Multiemployer pension fund withdrawal liability	(611)	(584)	22,602
Accounts payable, accrued expenses, and other liabilities	41,281	(27,039)	52,020
NET CASH PROVIDED BY OPERATING ACTIVITIES	205,989	170,364	255,347
INVESTING ACTIVITIES
Purchases of property, plant and equipment, net of financings	(43,248)	(90,955)	(43,992)
Proceeds from sale of property and equipment	13,348	13,490	4,256
Proceeds from sale of subsidiaries			4,680
Purchases of short-term investments	(165,133)	(129,709)	(108,495)
Proceeds from sale of short-term investments	216,735	120,409	58,698
Capitalization of internally developed software	(14,241)	(11,476)	(10,097)
NET CASH PROVIDED BY (USED IN) INVESTING ACTIVITIES	7,461	(98,241)	(94,950)
FINANCING ACTIVITIES
Borrowings under credit facilities	180,000
Borrowings under accounts receivable securitization program	45,000
Proceeds from notes payable		20,410
Payments on long-term debt	(326,098)	(58,938)	(71,260)
Net change in book overdrafts	6,510	(2,722)	262
Deferred financing costs		(562)	(202)
Payment of common stock dividends	(8,157)	(8,187)	(8,244)
Purchases of treasury stock	(6,595)	(9,110)	(9,404)
Payments for tax withheld on share-based compensation	(2,065)	(1,291)	(2,135)
NET CASH USED IN FINANCING ACTIVITIES	(111,405)	(60,400)	(90,983)
NET INCREASE IN CASH AND CASH EQUIVALENTS	102,045	11,723	69,414
Cash and cash equivalents at beginning of period	201,909	190,186	120,772
CASH AND CASH EQUIVALENTS CASH AT END OF PERIOD	303,954	201,909	190,186
NONCASH INVESTING ACTIVITIES
Equipment and other financings	61,803	70,372	94,016
Accruals for equipment received	1,667	234	$ 2,807
Lease liabilities arising from obtaining right-of-use assets	$ 67,819	$ 32,761