Consolidated Statements of Cash Flow Statement $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Statement of Cash Flows [Abstract]
Net Income (loss)	$ 27,421	$ (63,846)	$ 66,821	[1]
Adjustments to reconcile net income (loss) to cash provided by (used in) operating activities:
Depreciation	98,733	93,071	82,566
Amortization	13,168	20,485	26,463
Stock-based compensation expense	6,999	9,983	10,293
Gain on early extinguishment of debt	15,478	0	0
Provision for bad debts	3,934	(757)	(816)
Deferred tax expense (benefit)	(141,525)	(45,958)	34,086
Amortization of deferred financing costs	8,119	11,371	9,675
(Gain) loss on sale of assets	(121)	54	44,060
Changes in operating assets and liabilities:
Accounts receivable	8,525	(58,322)	(39,743)
Other current and long-term assets	(2,106)	2,272	(8,472)
Deferred drydocking charges	8,063	3,978	13,267
Accounts payable	9,405	(10,901)	(10,486)
Accrued liabilities and other liabilities	(11,044)	(11,935)	7,700
Accrued interest	(29)	(31)	(95)
Net cash provided by (used in) operating activities	(14,658)	53,500	217,095
CASH FLOWS FROM INVESTING ACTIVITIES:
Costs incurred for OSV newbuild program 5	18,104	76,277	190,070
Net proceeds from sale of assets	43	524	152,000
Vessel capital expenditures	1,687	20,689	86,792
Non-vessel capital expenditures	1,552	569	16,487
Net cash used in investing activities	(21,300)	(97,011)	(141,349)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from first-lien credit facility	66,640	0	0
Repurchase of senior notes	5,057	0	0
Repurchase of convertible notes	49,631	0	0
Deferred financing costs	5,636	1,102	2,089
Shares withheld for payment of employee withholding taxes	575	450	1,252
Shares withheld for payment of employee withholding taxes	485	1,300	3,112
Net cash provided by (used in) financing activities	6,226	(252)	(229)
Effects of exchange rate changes on cash	(446)	989	(839)
Net increase (decrease) in cash and cash equivalents	(30,178)	(42,774)	74,678
Cash and Cash Equivalents, at Carrying Value	186,849	217,027	259,801
SUPPLEMENTAL DISCLOSURES OF CASH FLOW ACTIVITIES:
Interest Paid	52,194	50,152	50,492
Proceeds from Income Tax Refunds	9,042
Income Taxes Paid		3,732	4,808
SUPPLEMENTAL DISCLOSURES OF NON-CASH FINANCING ACTIVITIES:
Exchange of convertible notes for first-lien term loan	$ 127,096	$ 0	$ 0

[1] The Company's net income for 2017 was favorably impacted by U.S. tax reform legislation that was enacted in December 2017. As a result of tax reform, the Company recorded a benefit of $125,225 related to the repricing of its deferred tax liabilities. Such benefits were reduced primarily by tax expense related to credits that may not be utilized prior to their expiration. Excluding these one-time tax items from the Company's December 31, 2017 results, its net loss would have been $(82,687) or $(2.24) per diluted share for the year ended December 31, 2017. See Note 9 for further information.