The end date of the period reflected on the cover page if a periodic report. For all other reports and registration statements containing historical data, it is the date up through which that historical data is presented. If there is no historical data in the report, use the filing date. The format of the date is YYYY-MM-DD.

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Debt Narrative (Details)										6 Months Ended
Debt Narrative (Details)	Jun. 27, 2019	May 24, 2019	May 21, 2019 USD ($)	Apr. 15, 2019 USD ($)	Nov. 16, 2018 USD ($)	Nov. 08, 2018	Oct. 03, 2018	Jul. 18, 2018 USD ($)	Oct. 25, 2017 USD ($)	Jun. 30, 2020 USD ($) numberOfVesselsCoveredByCreditFacility	Mar. 19, 2020	Dec. 31, 2019 USD ($)	Jul. 16, 2019
Debt Instrument [Line Items]
Total bank loans and senior notes, net										$ 652,204,000		$ 728,374,000
Notes Payable, Current										$ 71,049,000		75,276,000
Number of vessels										60
Document Period End Date										Jun. 30, 2020
Long-term Debt, Gross										$ 38,700,000
Short-term Debt										$ 71,049,000		75,276,000
Option to repurchase anniversary										third
Maximum [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Interest Rate During Period										5.90%
Minimum [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Interest Rate During Period										2.50%
Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross										$ 661,253,000		738,699,000
Minimum Net Worth Required for Compliance										$ 100,000,000.0
Percentage of the value any new Equity Issues after December 31, 2013										25.00%
Minimum Cumulative positive net income required for each fiscal quarter (as a percentage) for Net worth										50.00%
Minimum liquidity										$ 25,000,000.0
Minimum liquidity per owned vessels										$ 500,000
Minimum Fair value of the collateral of each credit facility										140.00%
Maximum Fair value of the collateral of each credit facility										160.00%
Minimum fair value vessel for financing obligations										115.00%
Secured Debt [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Ratio of Indebtedness to Net Capital										1.00
Consolidated Net worth required										$ 500,000,000.0
Secured Debt [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Ratio of Indebtedness to Net Capital										0.60
$90.0 Credit Facility [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross										$ 78,150,000		82,100,000
Debt Instrument, Basis Spread on Variable Rate						2.35%
Finance Leases Portfolio Segment [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Number of Assets sale leaseback													6
$30.0 Million Credit Facility [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross										$ 28,007,000		27,198,000
Debt Instrument, Basis Spread on Variable Rate										2.20%
$60.0 Million Credit Facility [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross										$ 25,442,000
$60.0 Million Credit Facility [Member] [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross												26,573,000
Debt Instrument, Basis Spread on Variable Rate										2.25%
$184.0 Million Credit Facility [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross										$ 71,591,000		130,145,000
Debt Instrument, Basis Spread on Variable Rate										2.40%
$34.0 Million Credit Facility [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross										$ 15,857,000		31,571,000
Debt Instrument, Basis Spread on Variable Rate							2.35%
$12.8 Million Credit Facility [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross										0		11,475,000
Long-term Debt, Gross										12.8
$12.5 Million Credit Facility [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross										0		8,617,000
Long-term Debt, Gross										12.5
$27.3 Million Credit Facility [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross										0		8,813,000
Long-term Debt, Gross										$ 27.3
$19.6 Lease - SBI Rumba [Member]
Debt Instrument [Line Items]
Option to repurchase anniversary										fifth
Virgo and Libra Lease [Member]
Debt Instrument [Line Items]
Option to repurchase anniversary										fourth
AVIC [Member]
Debt Instrument [Line Items]
Length of bareboat charter agreement	eight years
Option to repurchase anniversary										second
SBI Samba [Member] \| Finance Leases Portfolio Segment [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross										$ 19,679,000		20,384,000
SBI Rumba [Member] \| Finance Leases Portfolio Segment [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross										$ 16,253,000
Ultramax
Debt Instrument [Line Items]
Number of vessels \| numberOfVesselsCoveredByCreditFacility										33
Ultramax \| $90.0 Credit Facility [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Number of vessels										6
Ultramax \| $30.0 Million Credit Facility [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Number of vessels										0
Ultramax \| $60.0 Million Credit Facility [Member] [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Number of vessels										2
Ultramax \| $184.0 Million Credit Facility [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Number of vessels										6
Ultramax \| $34.0 Million Credit Facility [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Number of vessels										0
Kamsarmax \| $90.0 Credit Facility [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Number of vessels										0
Kamsarmax \| $30.0 Million Credit Facility [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Number of vessels										2
Kamsarmax \| $60.0 Million Credit Facility [Member] [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Number of vessels										0
Kamsarmax \| $184.0 Million Credit Facility [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Number of vessels										5
Kamsarmax \| $34.0 Million Credit Facility [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Number of vessels										2
Ultramax pool [Member] \| Finance Leases Portfolio Segment [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Years of amortization										5 years
Scrubber percentage of Market Value to be financed										82.00%
Scrubber percentage of price to be financed										82.00%
Ultramax pool [Member] \| AVIC [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Number of Assets sale leaseback													3
Ultramax pool [Member] \| $67.3 Million Lease Financing \| Secured Debt [Member]
Debt Instrument [Line Items]
Years of amortization										4 years
Number of Assets sale leaseback											2
CMBFL [Member] \| Finance Leases Portfolio Segment [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Length of bareboat charter agreement		seven
Number of Assets sale leaseback		7
Scrubber percentage of Market Value to be financed		75.00%
Scrubber percentage of price to be financed		75.00%
CMBFL [Member] \| Kamsarmax pool [Member] \| Finance Leases Portfolio Segment [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Number of Assets sale leaseback		4
CMBFL [Member] \| Ultramax pool [Member] \| Finance Leases Portfolio Segment [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Number of Assets sale leaseback		3
Virgo and Libra Lease [Member] \| Finance Leases Portfolio Segment [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Years of amortization second half			2 years
Years of amortization first half			2 years
Sale Leaseback Transaction, Net Proceeds, Financing Activities			$ 21,000,000.0
Length of bareboat charter agreement			11 years
SB Hermes [Member] \| Finance Leases Portfolio Segment [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Sale Leaseback Transaction, Net Proceeds, Financing Activities					$ 20,500,000
Sale Leaseback Transaction, Monthly Rental Payments					$ 177,938
Length of bareboat charter agreement					five
SBI Samba [Member] \| Finance Leases Portfolio Segment [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Sale Leaseback Transaction, Net Proceeds, Financing Activities				$ 21,400,000
Sale Leaseback Transaction, Monthly Rental Payments				$ 208,354
Length of bareboat charter agreement				five-year
SBI Tango [Member] \| Finance Leases Portfolio Segment [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Term of Bareboat Charter Agreement										5 years
Sale Leaseback Transaction, Net Proceeds, Financing Activities									$ 19,000,000.0
Sale Leaseback Transaction, Monthly Rental Payments								$ 164,250
SBI Echo [Member] \| Finance Leases Portfolio Segment [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Sale Leaseback Transaction, Net Proceeds, Financing Activities								19,000,000.0
Sale Leaseback Transaction, Monthly Rental Payments								$ 164,250
SBI Rumba [Member] \| Finance Leases Portfolio Segment [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Sale Leaseback Transaction, Net Proceeds, Financing Activities									19,600,000
Sale Leaseback Transaction, Monthly Rental Payments									$ 164,250
Optional period to extend Bareboat Charter									six months
SBI Echo [Member]
Debt Instrument [Line Items]
Length of bareboat charter agreement								five-year
SBI Rumba [Member]
Debt Instrument [Line Items]
Length of bareboat charter agreement									nine and a half year
Current [Domain] [Domain]
Debt Instrument [Line Items]
Bank loans and senior notes-current, net										$ 69,990,000		74,115,000
non-current [Domain]
Debt Instrument [Line Items]
Bank lloans and senior notes-non-current, net										$ 582,214,000		$ 654,259,000