v3.10.0.1

Leases - Additional Information (Details) | 1 Months Ended | 3 Months Ended | 9 Months Ended |
--- | --- | --- | --- | ---
Sep. 30, 2018 USD ($) vessel | Jul. 31, 2017 USD ($) vessel | Sep. 30, 2017 vessel | Sep. 30, 2018 USD ($) vessel | Sep. 30, 2017 USD ($) vessel | Dec. 31, 2017
Capital Leased Assets [Line Items] |  |  |  |  |  |
Proceeds from financing related to sales and leaseback of vessels | $ |  |  |  | $ 156,644,000 | $ 153,000,000 |
Aframax Tanker |  |  |  |  |  |
Capital Leased Assets [Line Items] |  |  |  |  |  |
Actual hull coverage ratio | 89.00% |  |  | 89.00% |  | 0.00%
Suezmax Tankers |  |  |  |  |  |
Capital Leased Assets [Line Items] |  |  |  |  |  |
Actual hull coverage ratio | 100.00% |  |  | 100.00% |  | 105.00%
Minimum | Suezmax and Aframax Tankers |  |  |  |  |  |
Capital Leased Assets [Line Items] |  |  |  |  |  |
Sale-leaseback, term of contract |  |  |  | 9 years |  |
Maximum | Suezmax and Aframax Tankers |  |  |  |  |  |
Capital Leased Assets [Line Items] |  |  |  |  |  |
Sale-leaseback, term of contract |  |  |  | 12 years |  |
Option to Purchase July 2020-2029 | Suezmax Tankers |  |  |  |  |  |
Capital Leased Assets [Line Items] |  |  |  |  |  |
Debt covenant minimum hull coverage ratio, Years 1, 2 and 3 |  |  |  | 90.00% |  |
Period required to maintain 90% hull coverage ratio |  |  |  | 3 years |  |
Minimum hull coverage ratios, thereafter |  |  |  | 100.00% |  |
Option to Purchase September 2020 to End of Term | Aframax Tanker |  |  |  |  |  |
Capital Leased Assets [Line Items] |  |  |  |  |  |
Minimum hull coverage ratios, thereafter |  |  |  | 90.00% |  |
Debt covenant minimum hull coverage ratio, Year 1 |  |  |  | 75.00% |  |
Debt covenant minimum hull coverage ratio, Year 2 |  |  |  | 78.00% |  |
Debt covenant minimum hull coverage ratio, Years 3 and 4 |  |  |  | 80.00% |  |
Capital Lease | Suezmax and Aframax Tankers |  |  |  |  |  |
Capital Leased Assets [Line Items] |  |  |  |  |  |
Minimum liquidity covenant requirement | $ | $ 35,000,000.0 |  |  | $ 35,000,000.0 |  |
Minimum liquidity as a percentage of consolidated debt covenant requirement | 5.00% |  |  | 5.00% |  |
Number of capital leases | vessel |  |  |  | 10 |  |
Commitments under the capital leases | $ | $ 445,300,000 |  |  | $ 445,300,000 |  |
Imputed interest | $ | 148,600,000 |  |  | $ 148,600,000 |  |
Capital Lease | Minimum | Suezmax and Aframax Tankers |  |  |  |  |  |
Capital Leased Assets [Line Items] |  |  |  |  |  |
Debt term |  |  |  | 6 months |  |
Aframax Tanker |  |  |  |  |  |
Capital Leased Assets [Line Items] |  |  |  |  |  |
Proceeds from financing related to sales and leaseback of vessels | $ | 156,600,000 |  |  |  |  |
Number of vessels sold | vessel |  |  | 3 |  | 3 |
Suezmax Tankers |  |  |  |  |  |
Capital Leased Assets [Line Items] |  |  |  |  |  |
Proceeds from financing related to sales and leaseback of vessels | $ |  | $ 153,000,000 |  |  |  |
Number of vessels sold | vessel |  |  | 2 |  | 2 |
Aframax Tankers Sale Leaseback |  |  |  |  |  |
Capital Leased Assets [Line Items] |  |  |  |  |  |
Proceeds from financing related to sales and leaseback of vessels | $ | $ 156,600,000 |  |  |  |  |
Number of vessels sold | vessel | 6 |  |  |  |  |
Aframax Tankers Sale Leaseback | Option to Purchase September 2020 to End of Term | Aframax Tanker |  |  |  |  |  |
Capital Leased Assets [Line Items] |  |  |  |  |  |
Number of vessels | vessel |  |  |  | 6 |  |
Suezmax Tanker Sale Leaseback |  |  |  |  |  |
Capital Leased Assets [Line Items] |  |  |  |  |  |
Proceeds from financing related to sales and leaseback of vessels | $ |  | $ 153,000,000 |  |  |  |
Suezmax Tanker Sale Leaseback | Option to Purchase July 2020-2029 | Suezmax Tankers |  |  |  |  |  |
Capital Leased Assets [Line Items] |  |  |  |  |  |
Number of vessels | vessel |  |  |  | 4 |  |
Number of vessels sold | vessel |  | 4 |  |  |  |
Suezmax Tanker Sale Leaseback | Suezmax Tankers |  |  |  |  |  |
Capital Leased Assets [Line Items] |  |  |  |  |  |
Number of vessels sold | vessel |  | 4 |  |  |  |

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