BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - ADDITIONAL INFORMATION (Details)		12 Months Ended
	Jan. 01, 2015 $ / T	Dec. 31, 2016 USD ($) $ / T	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($) $ / T
SPOT MARKET VOYAGE CHARTERS
Reserve against due from charterers		$ 1,900,000	$ 5,800,000
TIME CHARTERS
Accrual for unasserted claims relating to time charters		$ 400,000	500,000
VESSELS, NET
Estimated useful life of vessels		25 years
Estimated scrap value (in dollars per lightweight ton) | $ / T	325	325		265
Depreciation expense		$ 79,100,000	41,600,000	$ 42,400,000
Average period of scrap value of steel		15 years
Decrease in depreciation expense			2,800,000
Increase to net income per basic and diluted common share as a result of decrease in depreciation			0.05
VESSELS UNDER CONSTRUCTION
Capitalized interest costs		$ 27,602,000	35,170,000	8,958,000
GOODWILL
Goodwill		0	26,291,000	27,131,000
Goodwill impairment		23,297,000	0	2,099,000
Transfer to assets held for sale			840,000
Write-off related to sale of vessels		$ (2,994,000)		(1,249,000)
IMPAIRMENT OF LONG-LIVED ASSETS
Industry average trailing period considered for forecasting future charter rates and vessel operating costs		10 years
Impairment of vessel assets			520,000
Genmar Victory and Genmar Vision
GOODWILL
Write-off related to sale of vessels		$ (3,000,000)
MR tanker Gener8 Consul
GOODWILL
Transfer to assets held for sale			800,000
Vessels under construction.
VESSELS UNDER CONSTRUCTION
Capitalized interest costs		$ 27,600,000	$ 35,200,000	$ 9,000,000
Furniture, fixtures and equipment
OTHER FIXED ASSETS
Useful life		P10Y
Vessel Equipment
OTHER FIXED ASSETS
Useful life		P5Y
Vessel Equipment | Maximum
OTHER FIXED ASSETS
Useful life		P5Y
Computer Equipment
OTHER FIXED ASSETS
Useful life		P5Y