CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
OPERATING ACTIVITIES
Net income	$ 17,782	$ 29,264
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	56,140	51,722
Amortization of intangibles	1,959	2,249
Pension settlement expense	89	1,634
Share-based compensation expense	5,071	4,859
Provision for losses on accounts receivable	999	621
Change in deferred income taxes	(5,170)	5,124
Gain on sale of property and equipment and lease termination	(3,581)	(1,469)
Changes in operating assets and liabilities:
Receivables	9,626	1,781
Prepaid expenses	1,444	(3,323)
Other assets	4,358	(2,798)
Income taxes	8,413	(3,042)
Operating right-of-use assets and lease liabilities, net	(230)	159
Accounts payable, accrued expenses, and other liabilities	(14,833)	(6,310)
NET CASH PROVIDED BY OPERATING ACTIVITIES	82,067	80,471
INVESTING ACTIVITIES
Purchases of property, plant and equipment, net of financings	(16,209)	(41,909)
Proceeds from sale of property and equipment	7,670	3,798
Purchases of short-term investments	(97,493)	(43,327)
Proceeds from sale of short-term investments	46,725	33,332
Capitalization of internally developed software	(6,495)	(5,535)
NET CASH USED IN INVESTING ACTIVITIES	(65,802)	(53,641)
FINANCING ACTIVITIES
Borrowings under credit facilities	180,000
Borrowings under accounts receivable securitization program	45,000
Proceeds from notes payable		9,552
Payments on long-term debt	(29,185)	(29,984)
Net change in book overdrafts	615	(4,398)
Payment of common stock dividends	(4,082)	(4,102)
Purchases of treasury stock	(3,162)	(5,171)
Payments for tax withheld on share-based compensation	(1,070)	(1,182)
NET CASH PROVIDED BY (USED IN) FINANCING ACTIVITIES	188,116	(35,285)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	204,381	(8,455)
Cash and cash equivalent at beginning of period	201,909	190,186
CASH AND CASH EQUIVALENTS CASH AT END OF PERIOD	406,290	181,731
NONCASH INVESTING ACTIVITIES
Equipment financed	13,566	10,964
Accruals for equipment received	857	19,402
Lease liabilities arising from obtaining right-of-use assets	$ 23,727	$ 23,049