Condensed Consolidating Financial Information - Guarantor Subsidiaries - Condensed Consolidating Balance Sheets (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 29, 2017	Dec. 31, 2016	Dec. 31, 2015
Current Assets:
Cash and cash equivalents	$ 50,874	$ 8,770		$ 2,596	$ 2,407
Short-term investments	14,232	64,237
Accounts receivable - net	182,465	185,979
Inventories of spare parts – net	56,698	80,881
Prepaid expenses	11,419	11,475
Income taxes receivable	950	1,271
Total current assets	316,638	352,613
Property and equipment – net	902,485	946,765
Restricted cash and investments	19,781	12,396
Other assets	18,378	8,741
Deferred income taxes	4,944	3,309
Goodwill	0	61,299	$ 61,299
Intangibles	0	16,723
Total assets	1,262,226	1,401,846
Current Liabilities:
Senior Notes issued March 17, 2014	499,740	0
Accounts payable	50,289	37,186
Accrued and other current liabilities	45,292	41,850
Total current liabilities	595,321	79,036
Long-term debt	129,235	615,994
Deferred income taxes and other long-term liabilities	64,237	94,162
Shareholders’ Equity:
Common stock and paid-in capital	315,898	309,933
Accumulated other comprehensive loss	(3,952)	(280)
Retained earnings	161,487	303,001
Total shareholders’ equity	473,433	612,654		599,778	626,998
Total liabilities and shareholders’ equity	1,262,226	1,401,846
Parent Company Only (issuer) [Member]
Current Assets:
Cash and cash equivalents				36	46
Guarantor Subsidiaries [Member]
Current Assets:
Cash and cash equivalents				2,100	1,672
Non-Guarantor Subsidiaries [Member]
Current Assets:
Cash and cash equivalents				460	689
Reportable Legal Entities [Member] | Parent Company Only (issuer) [Member]
Current Assets:
Cash and cash equivalents	39,091	47
Short-term investments	14,232	64,237
Accounts receivable - net	64,416	90,077
Inventories of spare parts – net	43,933	68,737
Prepaid expenses	7,295	8,348
Income taxes receivable	394	345
Total current assets	169,361	231,791
Investment in subsidiaries and others	471,790	529,222
Property and equipment – net	576,763	617,488
Restricted cash and investments	19,781	12,382
Other assets	17,179	7,833
Total assets	1,254,874	1,398,716
Current Liabilities:
Senior Notes issued March 17, 2014	499,740
Accounts payable	44,089	28,130
Accrued and other current liabilities	25,158	23,147
Intercompany payable	74,336	113,387
Total current liabilities	643,323	164,664
Long-term debt	129,235	615,994
Deferred income taxes and other long-term liabilities	4,934	5,404
Shareholders’ Equity:
Common stock and paid-in capital	315,898	309,933
Accumulated other comprehensive loss	(3)	(280)
Retained earnings	161,487	303,001
Total shareholders’ equity	477,382	612,654
Total liabilities and shareholders’ equity	1,254,874	1,398,716
Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member]
Current Assets:
Cash and cash equivalents	1,259	1,072
Accounts receivable - net	93,060	74,886
Intercompany receivable	91,468	126,366
Inventories of spare parts – net	9,577	9,049
Prepaid expenses	2,520	1,898
Income taxes receivable	556	9
Total current assets	198,440	213,280
Property and equipment – net	287,375	284,984
Other assets	1,199	908
Total assets	487,014	499,172
Current Liabilities:
Accounts payable	4,587	4,636
Accrued and other current liabilities	12,335	10,577
Total current liabilities	16,922	15,213
Deferred income taxes and other long-term liabilities	58,752	84,300
Shareholders’ Equity:
Common stock and paid-in capital	77,951	77,951
Retained earnings	333,389	321,708
Total shareholders’ equity	411,340	399,659
Total liabilities and shareholders’ equity	487,014	499,172
Reportable Legal Entities [Member] | Non-Guarantor Subsidiaries [Member]
Current Assets:
Cash and cash equivalents	10,524	7,651
Accounts receivable - net	28,812	38,020
Inventories of spare parts – net	3,188	3,095
Prepaid expenses	1,604	1,229
Income taxes receivable		917
Total current assets	44,128	50,912
Property and equipment – net	38,347	44,293
Restricted cash and investments		14
Other assets	0	0
Deferred income taxes	4,944	3,309
Goodwill		61,299
Intangibles		16,723
Total assets	87,419	176,550
Current Liabilities:
Accounts payable	5,452	21,425
Accrued and other current liabilities	7,799	8,126
Intercompany payable	17,116	12,978
Total current liabilities	30,367	42,529
Deferred income taxes and other long-term liabilities	551	4,458
Shareholders’ Equity:
Common stock and paid-in capital	132,650	133,296
Accumulated other comprehensive loss	(3,949)
Retained earnings	(72,200)	(3,733)
Total shareholders’ equity	56,501	129,563
Total liabilities and shareholders’ equity	87,419	176,550
Eliminations [Member]
Current Assets:
Cash and cash equivalents				$ 0	$ 0
Accounts receivable - net	(3,823)	(17,004)
Intercompany receivable	(91,468)	(126,366)
Total current assets	(95,291)	(143,370)
Investment in subsidiaries and others	(471,790)	(529,222)
Total assets	(567,081)	(672,592)
Current Liabilities:
Accounts payable	(3,839)	(17,005)
Intercompany payable	(91,452)	(126,365)
Total current liabilities	(95,291)	(143,370)
Shareholders’ Equity:
Common stock and paid-in capital	(210,601)	(211,247)
Retained earnings	(261,189)	(317,975)
Total shareholders’ equity	(471,790)	(529,222)
Total liabilities and shareholders’ equity	$ (567,081)	$ (672,592)