v3.4.0.3
Condensed Consolidating Financial Information - Guarantor Subsidiaries - Condensed Consolidating Balance Sheets (Detail) - USD ($)
$ in Thousands
Mar. 31, 2016
Dec. 31, 2015
Mar. 31, 2015
Dec. 31, 2014
Current Assets:        
Cash $ 6,536 $ 2,407 $ 3,623 $ 6,270
Short-term investments 286,139 284,523    
Accounts receivable - net 151,388 144,778    
Inventories of spare parts - net 70,181 69,491    
Prepaid expenses 8,827 8,951    
Deferred income taxes 10,379 10,379    
Income taxes receivable 743 761    
Total current assets 534,193 521,290    
Property and equipment - net 908,414 883,529    
Restricted investments 15,336 15,336    
Other assets 6,330 5,243    
Total assets 1,464,273 1,425,398    
Current Liabilities:        
Accounts payable 61,620 31,373    
Accrued and other current liabilities 28,054 44,759    
Total current liabilities 89,674 76,132    
Long-term debt:        
Revolving credit facility 87,700 57,500    
Senior Notes dated March 17, 2014, net of debt issuance costs of $3,687 496,313 495,066    
Deferred income taxes and other long-term liabilities 171,049 169,702    
Shareholders' Equity:        
Common stock and paid-in capital 307,438 306,444    
Accumulated other comprehensive loss (90) (567)    
Retained earnings 312,189 321,121    
Total shareholders' equity 619,537 626,998 607,051 597,068
Total liabilities and shareholders' equity 1,464,273 1,425,398    
Parent Company Only (issuer) [Member]        
Current Assets:        
Cash 123 46 51 51
Short-term investments 286,139 284,523    
Accounts receivable - net 69,795 70,336    
Inventories of spare parts - net 60,998 60,060    
Prepaid expenses 6,191 7,162    
Deferred income taxes 10,379 10,379    
Income taxes receivable 985 1,002    
Total current assets 434,610 433,508    
Investment in subsidiaries 336,033 330,848    
Property and equipment - net 627,168 632,759    
Restricted investments 15,336 15,336    
Other assets 5,078 5,040    
Total assets 1,418,225 1,417,491    
Current Liabilities:        
Accounts payable 55,561 25,512    
Accrued and other current liabilities 18,594 29,138    
Intercompany payable 50,649 90,943    
Total current liabilities 124,804 145,593    
Long-term debt:        
Revolving credit facility 87,700 57,500    
Senior Notes dated March 17, 2014, net of debt issuance costs of $3,687 496,313 495,066    
Deferred income taxes and other long-term liabilities 89,871 92,334    
Shareholders' Equity:        
Common stock and paid-in capital 307,438 306,444    
Accumulated other comprehensive loss (90) (567)    
Retained earnings 312,189 321,121    
Total shareholders' equity 619,537 626,998    
Total liabilities and shareholders' equity 1,418,225 1,417,491    
Guarantor Subsidiaries [Member]        
Current Assets:        
Cash [1] 6,413 2,361 $ 3,572 $ 6,219
Accounts receivable - net [1] 81,593 74,442    
Intercompany receivable [1] 50,649 90,943    
Inventories of spare parts - net [1] 9,183 9,431    
Prepaid expenses [1] 2,636 1,789    
Income taxes receivable [1] (242) (241)    
Total current assets [1] 150,232 178,725    
Property and equipment - net [1] 281,246 250,770    
Other assets [1] 1,252 203    
Total assets [1] 432,730 429,698    
Current Liabilities:        
Accounts payable [1] 6,059 5,861    
Accrued and other current liabilities [1] 9,460 15,621    
Total current liabilities [1] 15,519 21,482    
Long-term debt:        
Deferred income taxes and other long-term liabilities [1] 81,178 77,368    
Shareholders' Equity:        
Common stock and paid-in capital [1] 79,191 79,061    
Retained earnings [1] 256,842 251,787    
Total shareholders' equity [1] 336,033 330,848    
Total liabilities and shareholders' equity [1] 432,730 429,698    
Eliminations [Member]        
Current Assets:        
Intercompany receivable (50,649) (90,943)    
Total current assets (50,649) (90,943)    
Investment in subsidiaries (336,033) (330,848)    
Total assets (386,682) (421,791)    
Current Liabilities:        
Intercompany payable (50,649) (90,943)    
Total current liabilities (50,649) (90,943)    
Shareholders' Equity:        
Common stock and paid-in capital (79,191) (79,061)    
Retained earnings (256,842) (251,787)    
Total shareholders' equity (336,033) (330,848)    
Total liabilities and shareholders' equity $ (386,682) $ (421,791)    
[1] Foreign subsidiaries represent minor subsidiaries and are included in the guarantor subsidiaries' amounts.