Debtor in Possession - Condensed Balance Sheet (Details) - USD ($) $ / shares in Units, $ in Thousands	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
Condensed Balance Sheet Statements Captions [Line Items]
Cash and cash equivalents	$ 21,882		$ 50,874	$ 5,852		$ 8,770
Short-term investments	76,141		14,232
Trade	174,499		168,459
Other	8,845		14,006
Inventories of spare parts – net	54,242		56,698
Prepaid expenses	13,072		11,419
Income taxes receivable	509		950
Total current assets	349,190		316,638
Property and equipment – net	885,669		902,485
Right of use assets	144,944
Restricted cash and investments	19,739		19,781
Other assets	20,937		18,378
Total assets	1,425,616		1,262,226
Accounts payable	70,615		50,289
Accrued and other current liabilities	38,483		45,292
Current portion of operating lease liabilities	27,535
Current maturities of long term debt	1,750		500,000
Total current liabilities	138,383		595,321
Term loan issued March 13, 2019, net of debt issuance costs of $5,254	62,996
Related party term loan issued September 28, 2018, net of debt issuance costs of $546 and $765, respectively	129,454		129,235
Deferred income taxes	51,964		59,178
Other long-term liabilities	3,673		5,059
Long-term operating lease liabilities	118,167
Total liabilities not subject to compromise	504,637		788,793
Liabilities subject to compromise	513,125
Total liabilities	1,017,762		788,793
Additional paid-in capital	316,143		314,316
Accumulated other comprehensive income (loss)	(4,040)		(3,952)
Retained earnings	94,169		161,487
Total shareholders’ equity	407,854	$ 439,508	473,433	591,565	$ 597,735	612,654
Total liabilities and shareholders’ equity	1,425,616		1,262,226
Note Payable, Related Party [Member]
Condensed Balance Sheet Statements Captions [Line Items]
Debt issuance costs	546		765
Term Loan [Member]
Condensed Balance Sheet Statements Captions [Line Items]
Debt issuance costs	5,254		260
Voting Common Stock [Member]
Condensed Balance Sheet Statements Captions [Line Items]
Common stock	$ 291		$ 291
Common stock, par value (in USD per share)	$ 0.10		$ 0.10
Common stock, shares authorized (shares)	12,500,000		12,500,000
Common stock, shares issued (shares)	2,905,757		2,905,757
Common stock, shares outstanding (shares)	2,905,757		2,905,757
Non-Voting Common Stock [Member]
Condensed Balance Sheet Statements Captions [Line Items]
Common stock	$ 1,291		$ 1,291
Total shareholders’ equity	$ 1,291	$ 1,291	$ 1,291	$ 1,291	$ 1,290	$ 1,289
Common stock, par value (in USD per share)	$ 0.10		$ 0.10
Common stock, shares authorized (shares)	37,500,000		37,500,000
Common stock, shares issued (shares)	12,919,681		12,919,681
Common stock, shares outstanding (shares)	12,919,681		12,919,681
Phi, Inc. and Debtors [Member]
Condensed Balance Sheet Statements Captions [Line Items]
Cash and cash equivalents	$ 10,310
Short-term investments	76,141
Trade	153,460
Other	6,120
Inventories of spare parts – net	50,800
Prepaid expenses	11,749
Income taxes receivable	509
Total current assets	309,089
Property and equipment – net	846,095
Right of use assets	127,821
Restricted cash and investments	19,739
Other assets	150,536
Total assets	1,453,280
Accounts payable	66,187
Accrued and other current liabilities	33,168
Current portion of operating lease liabilities	24,125
Current maturities of long term debt	1,750
Total current liabilities	125,230
Term loan issued March 13, 2019, net of debt issuance costs of $5,254	62,996
Related party term loan issued September 28, 2018, net of debt issuance costs of $546 and $765, respectively	129,454
Deferred income taxes	52,135
Other long-term liabilities	3,673
Long-term operating lease liabilities	104,491
Total liabilities not subject to compromise	477,979
Liabilities subject to compromise	513,125
Total liabilities	991,104
Additional paid-in capital	314,499
Accumulated other comprehensive income (loss)	(3)
Retained earnings	146,099
Total shareholders’ equity	462,176
Total liabilities and shareholders’ equity	1,453,280
Phi, Inc. and Debtors [Member] | Note Payable, Related Party [Member]
Condensed Balance Sheet Statements Captions [Line Items]
Debt issuance costs	546
Phi, Inc. and Debtors [Member] | Term Loan [Member]
Condensed Balance Sheet Statements Captions [Line Items]
Debt issuance costs	5,254
Phi, Inc. and Debtors [Member] | Voting Common Stock [Member]
Condensed Balance Sheet Statements Captions [Line Items]
Common stock	$ 291
Common stock, par value (in USD per share)	$ 0.10
Common stock, shares authorized (shares)	12,500,000
Common stock, shares issued (shares)	2,905,757
Common stock, shares outstanding (shares)	2,905,757
Phi, Inc. and Debtors [Member] | Non-Voting Common Stock [Member]
Condensed Balance Sheet Statements Captions [Line Items]
Common stock	$ 1,290
Common stock, par value (in USD per share)	$ 0.10
Common stock, shares authorized (shares)	37,500,000
Common stock, shares issued (shares)	12,919,681
Common stock, shares outstanding (shares)	12,919,681