Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
CASH FLOWS FROM OPERATING ACTIVITIES
Net earnings	$ 15,552	$ 39,310
Adjustments to reconcile net earnings to net cash provided by operating activities:
Depreciation and amortization	53,612	43,174
Equity-based compensation expense	403	7,716
Deferred tax expense	7,891	8,674
Employee benefit plans	(2,183)	(2,561)
Increase (Decrease) in Other Operating Assets and Liabilities, Net	1,267	259
Changes in working capital, net	23,742	(13,394)
Change in taxes receivable, net	4,229	14,107
Other Operating Activities, Cash Flow Statement	(914)	(870)
Net cash provided by operating activities	103,599	96,415
CASH FLOWS FROM INVESTING ACTIVITIES
Additions to plant and equipment	(85,709)	(57,394)
Payments for (Proceeds from) Other Investing Activities	417	250
Net cash used for investing activities	(85,292)	(57,144)
CASH FLOWS FROM FINANCING ACTIVITIES
Purchase of treasury stock	(4,875)	(35,168)
Proceeds from (Repayments of) Short-term Debt	117,000	477,169
Payments of Debt Issuance Costs	(144,000)	(477,169)
Payment of tax withholdings on equity-based payment arrangements	(790)
Proceeds from (Payments for) Other Financing Activities	(914)	(318)
Net cash (used for) provided by financing activities	(32,789)	(35,486)
Increase in cash	(14,482)	3,785
Cash at beginning of period	23,001	5,610
Cash at end of period	8,519	9,395
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION:
Cash paid for interest, net of amounts capitalized	14,310	13,368
Cash paid for income taxes	2,329	10,885
Cash received from income tax refunds	5,650	10,506
Changes in accrued plan and equipment	3,845	(2,841)
SUPPLEMENTAL DISCLOSURES OF NON-CASH INVESTING ACTIVITIES:
Unsettled Repurchases Of Common Stock	$ 4,525	$ 0