Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended		12 Months Ended
	Jan. 01, 2020	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Summary Of Significant Accounting Policies [Line Items]
Restricted cash and cash equivalents, noncurrent		$ 55,839	$ 32,313	$ 55,839	$ 32,313	$ 59,331
Allowance for doubtful accounts receivable		1,259		1,259		0
Provision for credit losses, net		(18)	0	1,259	41
Deferred finance costs, gross			14,524		14,524
Amortization of financing costs		1,264	$ 1,243	3,744	2,699
Cash paid to tax authority upon vesting of stock-based compensation				369	410
Increase in cash and cash equivalent				6,578	53,254
Repayments of advances from affiliated companies				4,836	95,987
Insurance claims proceeds related to vessel operations				967	$ 5,125
Property, Plant and Equipment, Net, Total		$ 1,284,758		$ 1,284,758		$ 1,330,795
Scenario, Forecast | Accounting Standards Update 2016-13 [Member]
Summary Of Significant Accounting Policies [Line Items]
Cumulative effect on retained earnings, net of tax	$ 500
10.75% Subordinated Notes [Member]
Summary Of Significant Accounting Policies [Line Items]
Debt instrument, interest rate, stated percentage		10.75%		10.75%
8.5% Senior Notes [Member]
Summary Of Significant Accounting Policies [Line Items]
Debt instrument, interest rate, stated percentage		8.50%		8.50%
Accounts Receivable [Member]
Summary Of Significant Accounting Policies [Line Items]
Concentration risk, percentage				86.00%		88.00%
Term Loan [Member] | 2017 Term Loan Facility, Sinosure Credit Facility, ABN Term Loan Facility, 8.5% Senior Notes and 10.75% Subordinated Notes [Member]
Summary Of Significant Accounting Policies [Line Items]
Deferred finance costs, gross		$ 21,035		$ 21,035		$ 26,647
Revolving Credit Facility [Member] | INSW Facilities [Member]
Summary Of Significant Accounting Policies [Line Items]
Deferred finance costs, gross		$ 309		$ 309		$ 413