CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018		Sep. 30, 2017
OPERATING ACTIVITIES
Net income	$ 162,040		$ 104,808
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization and other non-cash charges	123,281		127,679
Stock-based compensation expense	7,204		9,019
Gain on disposition of assets, net	(3,459)		(5,779)
Gain on insurance recovery	(9,646)
Gain on benefit plan financing arrangement	(1,020)
Deferred income tax provision (benefit)	6,319		(28,163)
(Increase) decrease in assets:
Accounts receivable	(5,029)		(206,201)
Income taxes receivable	28,664		54,033
Inventories	(14,233)		(4,730)
Prepaid expenses	2,647		1,134
Other current assets	1,420		(2,037)
Other non-current assets	(2,106)		(3,135)
Increase (decrease) in liabilities:
Accounts payable	21,852		47,151
Income taxes payable	1,775		(728)
Accrued payroll and related expenses	8,583		13,088
Accrued insurance expenses	604		125
Accrued state, local and other taxes	(1,545)		4,612
Other accrued expenses	(873)		(5,385)
Pension liabilities	(4,700)		2,708
Long-term accrued insurance expenses	1,059		783
Other long-term liabilities	(885)		309
Net cash provided by operating activities	321,952		109,291
INVESTING ACTIVITIES
Capital expenditures	(199,581)		(75,016)
Proceeds from sale of assets	10,102		10,532
Proceeds from insurance recovery	9,646
Proceeds from benefit plan financing arrangement	2,218
Re-investment in benefit plan financing arrangement	(2,218)
Net cash used for investing activities	(179,833)		(64,484)
FINANCING ACTIVITIES
Payment of dividends	(64,636)		(13,026)
Cash paid for common stock purchased and retired	(40,160)		(26,724)
Net cash used for financing activities	(104,796)		(39,750)
Net increase in cash and cash equivalents	37,323		5,057
Cash and cash equivalents at beginning of period	91,050	[1]	131,835
Cash and cash equivalents at end of period	128,373		136,892
Supplemental cash flows disclosure:
Interest paid, net of amounts capitalized	309		192
Income taxes paid, net	1,781		39,775
Supplemental disclosure of noncash investing activities:
Capital expenditures included in accounts payable	$ 8,960		$ 7,552

[1] (Note 1)