Long-Term Debt	9 Months Ended
Sep. 30, 2017
Long-term Debt and Capital Lease Obligations [Abstract]
Long-Term Debt	5. LONG-TERM DEBT SEACOR’s Board of Directors previously approved a securities repurchase plan that authorizes the Company to acquire SEACOR common stock, par value $0.01 per share (“Common Stock”), 7.375% Senior Notes, 3.0% Convertible Senior Notes, and 2.5% Convertible Senior Notes (collectively the “Securities”) through open market purchases, privately negotiated transactions or otherwise, depending on market conditions. As of September 30, 2017, the Company’s remaining repurchase authority for the Securities was $77.4 million. 3.0% Convertible Senior Notes. In connection with the Spin-off, the conversion rate of the 3.0% Convertible Senior Notes was adjusted to 12.1789. The Company has reserved the maximum number of shares of Common Stock needed for conversion, or 2,801,147 shares as of September 30, 2017. 2.5% Convertible Senior Notes. During the nine months ended September 30, 2017, the Company repurchased $61.7 million in principal amount of its 2.5% Convertible Senior Notes for total consideration of $61.9 million. Consideration of $60.5 million was allocated to the settlement of the long-term debt resulting in debt extinguishment gains of $0.1 million included in the accompanying condensed consolidated statements of income (loss). Consideration of $1.4 million was allocated to the purchase of the conversion option embedded in the 2.5% Convertible Senior Notes as included in the accompanying consolidated statements of changes in equity. As of September 30, 2017, the remaining principal amount outstanding of $95.5 million is included in current liabilities as the holders may require the Company to repurchase these notes on December 19, 2017. In connection with the Spin-off, the conversion rate of the 2.5% Convertible Senior Notes was adjusted to 18.4176. The Company has reserved the maximum number of shares of Common Stock needed for conversion, or 1,758,107 shares as of September 30, 2017. 7.375% Senior Notes. During the nine months ended September 30, 2017, the Company repurchased $7.6 million in principal amount of its 7.375% Senior Notes for $7.7 million resulting in debt extinguishment losses of $0.2 million included in the accompanying condensed consolidated statements of income (loss). The outstanding principal amount of these notes outstanding was $153.1 million as of September 30, 2017. SEA-Vista Credit Facility. During the nine months ended September 30, 2017, SEA-Vista borrowed $38.9 million and repaid $45.9 million on the Revolving Loan and made scheduled repayments of $3.6 million on the Term A-1 Loan and $3.0 million on the Term A-2 Loan. As of September 30, 2017, SEA-Vista had $21.0 million of remaining borrowing capacity under the Revolving Loan. Subsequent to September 30, 2017, SEA-Vista borrowed $6.0 million on the Revolving Loan. ISH Credit Facility. On July 3, 2017, ISH emerged from bankruptcy pursuant to the Plan (see Note 2). In conjunction with the emergence under the Plan, ISH assumed debt of $25.0 million under a credit facility that matures in July 2020. The facility consists of two tranches: (i) a $5.0 million revolving credit facility (the “ISH Revolving Loan”) and (ii) a $20.0 million term loan (the “ISH Term Loan”) (collectively the “ISH Credit Facility”). ISH incurred $0.1 million of issuance costs. The proceeds from this facility will be used for general working capital purposes and payments to ISH’s creditors in accordance with the Plan. During the nine months ended September 30, 2017, ISH repaid $7.2 million on the ISH Term Loan and $5.0 million on the ISH Revolving Loan. Both loans bear interest at a variable rate of either LIBOR multiplied by the Statutory Reserve Rate or Prime Rate plus an applicable margin, as defined in the ISH Credit Facility. A quarterly fee of 0.5% is payable on the unused commitment of the ISH Revolving Loan. Beginning September 30, 2017, ISH is required to make quarterly prepayments on the ISH Term Loan of $0.7 million. Commencing with the calendar year ending December 31, 2018, ISH is required to make annual prepayments on the ISH Term Loan in an amount equal to 50% of excess cash flow as defined in the credit agreement. The ISH Credit Facility contains various financial and restrictive covenants including indebtedness to EBITDA and adjusted EBITDA to interest expense maintenance, as defined in the ISH Credit Facility. The ISH Credit Facility is non-recourse to SEACOR and its subsidiaries other than ISH. As of September 30, 2017, the ISH Credit Facility had $5.0 million of remaining borrowing capacity under the ISH Revolving Loan. Other. During the nine months ended September 30, 2017 the Company acquired $3.9 million of debt related to the ISH acquisition (see Note 2). This debt bears interest at 7.0% and is collateralized by certain acquired assets. During the nine months ended September 30, 2017, the Company made scheduled payments on other long-term debt of $0.3 million. Letters of Credit. As of September 30, 2017, the Company had outstanding letters of credit totaling $27.2 million with various expiration dates through 2019, including $16.7 million that have been issued on behalf of SEACOR Marine. Guarantees. The Company has guaranteed the payments of amounts owed under certain sale-leaseback transactions, equipment financing and multi-employer pension obligations on behalf of SEACOR Marine. As of September 30, 2017, these guarantees on behalf of SEACOR Marine totaled $84.9 million and decline as payments are made on the outstanding obligations. The Company earns a fee of 50 basis points per annum on these guarantees and outstanding letters of credit. For the three and nine months ended September 30, 2017, the Company earned fees of $0.1 million and $0.5 million, respectively. For the three and nine months ended September 30, 2016, the Company earned fees of $0.1 million and $0.6 million, respectively.

5. LONG-TERM DEBT

SEACOR’s Board of Directors previously approved a securities repurchase plan that authorizes the Company to acquire SEACOR common stock, par value $0.01 per share (“Common Stock”), 7.375% Senior Notes, 3.0% Convertible Senior Notes, and 2.5% Convertible Senior Notes (collectively the “Securities”) through open market purchases, privately negotiated transactions or otherwise, depending on market conditions. As of September 30, 2017, the Company’s remaining repurchase authority for the Securities was $77.4 million.

3.0% Convertible Senior Notes. In connection with the Spin-off, the conversion rate of the 3.0% Convertible Senior Notes was adjusted to 12.1789. The Company has reserved the maximum number of shares of Common Stock needed for conversion, or 2,801,147 shares as of September 30, 2017.

2.5% Convertible Senior Notes. During the nine months ended September 30, 2017, the Company repurchased $61.7 million in principal amount of its 2.5% Convertible Senior Notes for total consideration of $61.9 million. Consideration of $60.5 million was allocated to the settlement of the long-term debt resulting in debt extinguishment gains of $0.1 million included in the accompanying condensed consolidated statements of income (loss). Consideration of $1.4 million was allocated to the purchase of the conversion option embedded in the 2.5% Convertible Senior Notes as included in the accompanying consolidated statements of changes in equity. As of September 30, 2017, the remaining principal amount outstanding of $95.5 million is included in current liabilities as the holders may require the Company to repurchase these notes on December 19, 2017.

In connection with the Spin-off, the conversion rate of the 2.5% Convertible Senior Notes was adjusted to 18.4176. The Company has reserved the maximum number of shares of Common Stock needed for conversion, or 1,758,107 shares as of September 30, 2017.

7.375% Senior Notes. During the nine months ended September 30, 2017, the Company repurchased $7.6 million in principal amount of its 7.375% Senior Notes for $7.7 million resulting in debt extinguishment losses of $0.2 million included in the accompanying condensed consolidated statements of income (loss). The outstanding principal amount of these notes outstanding was $153.1 million as of September 30, 2017.

SEA-Vista Credit Facility. During the nine months ended September 30, 2017, SEA-Vista borrowed $38.9 million and repaid $45.9 million on the Revolving Loan and made scheduled repayments of $3.6 million on the Term A-1 Loan and $3.0 million on the Term A-2 Loan. As of September 30, 2017, SEA-Vista had $21.0 million of remaining borrowing capacity under the Revolving Loan. Subsequent to September 30, 2017, SEA-Vista borrowed $6.0 million on the Revolving Loan.

ISH Credit Facility. On July 3, 2017, ISH emerged from bankruptcy pursuant to the Plan (see Note 2). In conjunction with the emergence under the Plan, ISH assumed debt of $25.0 million under a credit facility that matures in July 2020. The facility consists of two tranches: (i) a $5.0 million revolving credit facility (the “ISH Revolving Loan”) and (ii) a $20.0 million term loan (the “ISH Term Loan”) (collectively the “ISH Credit Facility”). ISH incurred $0.1 million of issuance costs. The proceeds from this facility will be used for general working capital purposes and payments to ISH’s creditors in accordance with the Plan. During the nine months ended September 30, 2017, ISH repaid $7.2 million on the ISH Term Loan and $5.0 million on the ISH Revolving Loan.

Both loans bear interest at a variable rate of either LIBOR multiplied by the Statutory Reserve Rate or Prime Rate plus an applicable margin, as defined in the ISH Credit Facility. A quarterly fee of 0.5% is payable on the unused commitment of the ISH Revolving Loan. Beginning September 30, 2017, ISH is required to make quarterly prepayments on the ISH Term Loan of $0.7 million. Commencing with the calendar year ending December 31, 2018, ISH is required to make annual prepayments on the ISH Term Loan in an amount equal to 50% of excess cash flow as defined in the credit agreement.

The ISH Credit Facility contains various financial and restrictive covenants including indebtedness to EBITDA and adjusted EBITDA to interest expense maintenance, as defined in the ISH Credit Facility. The ISH Credit Facility is non-recourse to SEACOR and its subsidiaries other than ISH. As of September 30, 2017, the ISH Credit Facility had $5.0 million of remaining borrowing capacity under the ISH Revolving Loan.

Other. During the nine months ended September 30, 2017 the Company acquired $3.9 million of debt related to the ISH acquisition (see Note 2). This debt bears interest at 7.0% and is collateralized by certain acquired assets. During the nine months ended September 30, 2017, the Company made scheduled payments on other long-term debt of $0.3 million.

Letters of Credit. As of September 30, 2017, the Company had outstanding letters of credit totaling $27.2 million with various expiration dates through 2019, including $16.7 million that have been issued on behalf of SEACOR Marine.

Guarantees. The Company has guaranteed the payments of amounts owed under certain sale-leaseback transactions, equipment financing and multi-employer pension obligations on behalf of SEACOR Marine. As of September 30, 2017, these guarantees on behalf of SEACOR Marine totaled $84.9 million and decline as payments are made on the outstanding obligations.

The Company earns a fee of 50 basis points per annum on these guarantees and outstanding letters of credit. For the three and nine months ended September 30, 2017, the Company earned fees of $0.1 million and $0.5 million, respectively. For the three and nine months ended September 30, 2016, the Company earned fees of $0.1 million and $0.6 million, respectively.