Consolidated Statement Of Shareholder's Equity - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Earnings [Member]	Non-controlling Interests [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			87,962	12,390	$ 100,352
Member distribution to non-controlling interest holder				(9,800)	(9,800)
Dividends to shareholders			(44,841)		(44,841)
Repurchase and retirement of Comon Stock, value	(3)	(3,997)			$ (4,000)
Repurchase and retirement of Comon Stock, shares					(288,532)
Ending balance at Dec. 31, 2018	744	270,369	158,641	45,611	$ 475,365
Ending balance, shares at Dec. 31, 2018					74,445,923
Net income			34,851	11,273	$ 46,124
Member distribution to non-controlling interest holder				(7,350)	(7,350)
Dividends to shareholders			(47,645)		(47,645)
Repurchase and retirement of Comon Stock, value		835			$ 835
Repurchase and retirement of Comon Stock, shares					(83,230)
Ending balance at Dec. 31, 2019	744	269,534	145,847	49,534	$ 465,659
Ending balance, shares at Dec. 31, 2019					74,362,693
Net income			8,225	7,392	$ 15,617
Member distribution to non-controlling interest holder				(4,900)	(4,900)
Dividends to shareholders			(95,923)		(95,923)
Repurchase and retirement of Comon Stock, value	(19)	(11,722)			$ (11,741)
Repurchase and retirement of Comon Stock, shares					(1,878,400)
Ending balance at Dec. 31, 2020	$ 725	$ 257,812	$ 58,149	$ 52,026	$ 368,712
Ending balance, shares at Dec. 31, 2020					72,484,293