Consolidated Statement Of Shareholder's Equity - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-In-Capital [Member]	Retained Earnings [Member]	Equity Attributable To Non-Controlling Interest [Member]	Total
Beginning balance at Dec. 31, 2017	$ 747	$ 274,366	$ 115,520	$ 43,021	$ 433,654
Beginning balance, shares at Dec. 31, 2017	74,734,455
Net income (loss)			20,975	2,607	23,582
Dividends to shareholders			(11,210)		(11,210)
Ending balance at Mar. 31, 2018	$ 747	274,366	125,285	45,628	446,026
Ending balance, shares at Mar. 31, 2018	74,734,455
Beginning balance at Dec. 31, 2017	$ 747	274,366	115,520	43,021	433,654
Beginning balance, shares at Dec. 31, 2017	74,734,455
Net income (loss)					77,682
Ending balance at Sep. 30, 2018	$ 747	274,366	150,062	47,630	472,805
Ending balance, shares at Sep. 30, 2018	74,734,455
Beginning balance at Mar. 31, 2018	$ 747	274,366	125,285	45,628	446,026
Beginning balance, shares at Mar. 31, 2018	74,734,455
Net income (loss)			26,710	3,317	30,027
Dividends to shareholders			(11,210)		(11,210)
Ending balance at Jun. 30, 2018	$ 747	274,366	140,785	48,945	464,843
Ending balance, shares at Jun. 30, 2018	74,734,455
Net income (loss)			20,488	3,585	24,073
Distributions to non-controlling interest				(4,900)	(4,900)
Dividends to shareholders			(11,211)		(11,211)
Ending balance at Sep. 30, 2018	$ 747	274,366	150,062	47,630	472,805
Ending balance, shares at Sep. 30, 2018	74,734,455
Beginning balance at Dec. 31, 2018	$ 744	270,369	158,641	45,611	475,365
Beginning balance, shares at Dec. 31, 2018	74,445,923
Net income (loss)			15,153	1,716	16,869
Dividends to shareholders			(12,655)		(12,655)
Ending balance at Mar. 31, 2019	$ 744	270,369	161,139	47,327	479,579
Ending balance, shares at Mar. 31, 2019	74,445,923
Beginning balance at Dec. 31, 2018	$ 744	270,369	158,641	45,611	475,365
Beginning balance, shares at Dec. 31, 2018	74,445,923
Net income (loss)					33,392
Ending balance at Sep. 30, 2019	$ 744	270,369	144,971	54,706	470,790
Ending balance, shares at Sep. 30, 2019	74,445,923
Beginning balance at Mar. 31, 2019	$ 744	270,369	161,139	47,327	479,579
Beginning balance, shares at Mar. 31, 2019	74,445,923
Net income (loss)			(11,183)	5,131	(6,052)
Dividends to shareholders			(12,657)		(12,657)
Ending balance at Jun. 30, 2019	$ 744	270,369	137,299	52,458	460,870
Ending balance, shares at Jun. 30, 2019	74,445,923
Net income (loss)			20,327	2,248	22,575
Dividends to shareholders			(12,655)		(12,655)
Ending balance at Sep. 30, 2019	$ 744	$ 270,369	$ 144,971	$ 54,706	$ 470,790
Ending balance, shares at Sep. 30, 2019	74,445,923