BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - NATURE OF BUSINESS (Details)	6 Months Ended
Jun. 30, 2017 segment building item
NATURE OF BUSINESS
Number of tankers	39
Number of tankers in operation	38
Number of operating segments \| segment	1
VLCCs
NATURE OF BUSINESS
Number of tankers	24
New building construction \| building	1
Suezmax
NATURE OF BUSINESS
Number of tankers	9
Aframax
NATURE OF BUSINESS
Number of tankers	3
Panamax
NATURE OF BUSINESS
Number of tankers	2
Navig8 Limited
NATURE OF BUSINESS
Ownership percentage in outstanding common shares (as a percent)	4.00%

Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

No definition available.

Name:	us-gaap_NumberOfOperatingSegments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration