CONDENSED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Cash flows from operating activities:
Net earnings	$ 27,645	$ 38,484
Adjustments to reconcile net earnings to net cash provided by operations:
Depreciation and amortization	48,170	48,624
Provision for deferred income taxes	8,562	14,713
Amortization of unearned share-based compensation	2,693	2,584
Amortization of major maintenance costs	5,034	4,608
Amortization of debt issuance costs	200	200
Other	1,038	(342)
Increase (decrease) in cash flows resulting from changes in operating assets and liabilities, net	(8,140)	4,360
Net cash provided by operating activities	85,202	113,231
Cash flows from investing activities:
Capital expenditures	(45,765)	(50,523)
Proceeds from disposition of assets	7,958	297
Net cash used in investing activities	(37,807)	(50,226)
Cash flows from financing activities:
Payments on bank credit facilities, net	(48,451)	(62,886)
Proceeds from exercise of stock options	1,258	0
Purchase of treasury stock	0	(1,827)
Payments related to tax withholding for share-based compensation	(2,873)	(1,749)
Other	(207)	(711)
Net cash used in financing activities	(50,273)	(67,173)
Decrease in cash and cash equivalents	(2,878)	(4,168)
Cash and cash equivalents, beginning of year	5,634	5,885
Cash and cash equivalents, end of period	2,756	1,717
Supplemental disclosures of cash flow information:
Interest paid	8,856	8,743
Income taxes paid (refunded)	1,686	(412)
Capital expenditures included in accounts payable	$ (1,778)	$ (987)