Supplemental Guarantor Financial Information Condensed Consolidating Statement of Cash Flows (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
CASH FLOWS FROM OPERATING ACTIVITIES
Net earnings (loss)	$ 901	$ 23,064	$ 40,211	$ 44,418
Adjustments to reconcile net earnings to net cash provided by (used in) operating activities:
Depreciation and amortization	22,747	21,204	65,921	62,844
Equity-based compensation expense			9,826	2,495
Deferred tax expense (benefit)			12,329	(12,403)
Employee benefit plans			(500)	2,122
Amortization of Financing Costs and Discounts			637	714
Gain (Loss) on Disposition of Assets			30	1,109
Non-cash adjustments to unrecognized taxes			(153)	(1,123)
Changes in working capital, net			4,045	15,471
Change in taxes receivable, net			7,217	1,255
Excess tax benefits from equity share-based payment arrangements			(157)	(3,848)
Funding of qualified pension plans			0	(3,179)
Other Operating Activities, Cash Flow Statement			(523)	(2,320)
Net cash provided by operating activities			138,883	107,555
CASH FLOWS FROM INVESTING ACTIVITIES
Change in short-term investments, net			250	40,000
Additions to plant and equipment			(105,514)	(78,461)
Proceeds from Sale of Productive Assets			0	587
Net cash used for investing activities			(105,264)	(37,874)
CASH FLOWS FROM FINANCING ACTIVITIES
Payments for Repurchase of Common Stock			(51,528)	(84,305)
Investment (to) from Parent			0	0
Proceeds from Lines of Credit			944,844	0
Repayments of Lines of Credit			(931,832)	0
Payment of tax withholdings on equity-based payment arrangements			(488)	(3,129)
Excess Tax Benefit from Share-based Compensation, Financing Activities			157	3,848
Proceeds from (Payments for) Other Financing Activities			(51)	(9)
Net cash (used for) provided by financing activities			(38,898)	(83,595)
Increase in cash			(5,279)	(13,914)
Cash at beginning of period			5,610	27,331
Cash at end of period	331	13,417	331	13,417
Issuer
CASH FLOWS FROM OPERATING ACTIVITIES
Net earnings (loss)	901	27,701	40,211	45,363
Adjustments to reconcile net earnings to net cash provided by (used in) operating activities:
Depreciation and amortization			50,214	47,854
Equity-based compensation expense			9,826	2,495
Deferred tax expense (benefit)			11,641	(14,631)
Employee benefit plans			(500)	2,122
Amortization of Financing Costs and Discounts			637	714
Gain (Loss) on Disposition of Assets			30	1,203
Non-cash adjustments to unrecognized taxes			(166)	(1,126)
Changes in working capital, net			1,961	15,656
Change in taxes receivable, net			6,178	6,760
Excess tax benefits from equity share-based payment arrangements			(157)	(3,848)
Funding of qualified pension plans				(3,179)
Other Operating Activities, Cash Flow Statement			(1,048)	(1,261)
Net cash provided by operating activities			118,827	98,122
CASH FLOWS FROM INVESTING ACTIVITIES
Change in short-term investments, net			250	40,000
Additions to plant and equipment			(99,912)	(74,002)
Proceeds from Sale of Productive Assets				0
Net cash used for investing activities			(99,662)	(34,002)
CASH FLOWS FROM FINANCING ACTIVITIES
Payments for Repurchase of Common Stock			(51,528)	(84,305)
Investment (to) from Parent			14,454	5,561
Proceeds from Lines of Credit			944,844
Repayments of Lines of Credit			(931,832)
Payment of tax withholdings on equity-based payment arrangements			(488)	(3,129)
Excess Tax Benefit from Share-based Compensation, Financing Activities			157	3,848
Proceeds from (Payments for) Other Financing Activities			(51)	(9)
Net cash (used for) provided by financing activities			(24,444)	(78,034)
Increase in cash			(5,279)	(13,914)
Cash at beginning of period			5,610	27,331
Cash at end of period	331	13,417	331	13,417
Guarantor Subsidiaries
CASH FLOWS FROM OPERATING ACTIVITIES
Net earnings (loss)	2,304	8,476	4,607	1,677
Adjustments to reconcile net earnings to net cash provided by (used in) operating activities:
Depreciation and amortization			15,707	14,990
Equity-based compensation expense			0	0
Deferred tax expense (benefit)			1,826	150
Employee benefit plans			0	0
Amortization of Financing Costs and Discounts			0	0
Gain (Loss) on Disposition of Assets			0	(94)
Non-cash adjustments to unrecognized taxes			13	3
Changes in working capital, net			4,531	(185)
Change in taxes receivable, net			(1,408)	(15,758)
Excess tax benefits from equity share-based payment arrangements			0	0
Funding of qualified pension plans				0
Other Operating Activities, Cash Flow Statement			(613)	(1,059)
Net cash provided by operating activities			24,663	(276)
CASH FLOWS FROM INVESTING ACTIVITIES
Change in short-term investments, net			0	0
Additions to plant and equipment			(5,602)	(4,459)
Proceeds from Sale of Productive Assets				587
Net cash used for investing activities			(5,602)	(3,872)
CASH FLOWS FROM FINANCING ACTIVITIES
Payments for Repurchase of Common Stock			0	0
Investment (to) from Parent			(19,061)	4,148
Proceeds from Lines of Credit			0
Repayments of Lines of Credit			0
Payment of tax withholdings on equity-based payment arrangements			0	0
Excess Tax Benefit from Share-based Compensation, Financing Activities			0	0
Proceeds from (Payments for) Other Financing Activities			0	0
Net cash (used for) provided by financing activities			(19,061)	4,148
Increase in cash			0	0
Cash at beginning of period			0	0
Cash at end of period	0	0	0	0
Eliminations
CASH FLOWS FROM OPERATING ACTIVITIES
Net earnings (loss)	(2,304)	(13,113)	(4,607)	(2,622)
Adjustments to reconcile net earnings to net cash provided by (used in) operating activities:
Depreciation and amortization			0	0
Equity-based compensation expense			0	0
Deferred tax expense (benefit)			(1,138)	2,078
Employee benefit plans			0	0
Amortization of Financing Costs and Discounts			0	0
Gain (Loss) on Disposition of Assets			0	0
Non-cash adjustments to unrecognized taxes			0	0
Changes in working capital, net			(2,447)	0
Change in taxes receivable, net			2,447	10,253
Excess tax benefits from equity share-based payment arrangements			0	0
Funding of qualified pension plans				0
Other Operating Activities, Cash Flow Statement			1,138	0
Net cash provided by operating activities			(4,607)	9,709
CASH FLOWS FROM INVESTING ACTIVITIES
Change in short-term investments, net			0	0
Additions to plant and equipment			0	0
Proceeds from Sale of Productive Assets				0
Net cash used for investing activities			0	0
CASH FLOWS FROM FINANCING ACTIVITIES
Payments for Repurchase of Common Stock			0	0
Investment (to) from Parent			4,607	(9,709)
Proceeds from Lines of Credit			0
Repayments of Lines of Credit			0
Payment of tax withholdings on equity-based payment arrangements			0	0
Excess Tax Benefit from Share-based Compensation, Financing Activities			0	0
Proceeds from (Payments for) Other Financing Activities			0	0
Net cash (used for) provided by financing activities			4,607	(9,709)
Increase in cash			0	0
Cash at beginning of period			0	0
Cash at end of period	$ 0	$ 0	$ 0	$ 0