Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Current Assets:
Cash	$ 16,453	$ 8,770
Short-term investments	30,509	64,237
Accounts receivable – net
Trade	175,372	168,153
Other	22,035	17,826
Inventories of spare parts – net	74,352	80,881
Prepaid expenses	13,201	11,475
Income taxes receivable	649	1,271
Total current assets	332,571	352,613
Property and equipment – net	923,577	946,765
Restricted investments	19,781	12,396
Other assets	10,142	8,741
Deferred income taxes	1,009	3,309
Goodwill	61,299	61,299
Intangibles	15,557	16,723
Total assets	1,363,936	1,401,846
Current Liabilities:
Senior Notes issued March 17, 2014, net of debt issuance costs of $571	499,429	0
Accounts payable	39,209	37,186
Accrued and other current liabilities	39,557	41,850
Total current liabilities	578,195	79,036
Long-term debt:
Revolving credit facility	0	117,500
Senior Notes issued March 17, 2014, net of debt issuance costs of $1,506	0	498,494
Related Party Term Loan issued September 28, 2018, net of debt issuance costs of $874	129,126	0
Deferred income taxes	74,062	86,005
Other long-term liabilities	5,168	8,157
Commitments and contingencies (Note 9)
Shareholders’ Equity:
Additional paid-in capital	312,503	308,353
Accumulated other comprehensive income (loss)	(4,094)	(280)
Retained earnings	267,394	303,001
Total shareholders’ equity	577,385	612,654
Total liabilities and shareholders’ equity	1,363,936	1,401,846
Voting Common Stock [Member]
Shareholders’ Equity:
Common stock	291	291
Non-Voting Common Stock [Member]
Shareholders’ Equity:
Common stock	1,291	1,289
Total shareholders’ equity	$ 1,291	$ 1,289