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, 2016						$ 298,311
Net income						139,343
Ending balance at Dec. 31, 2017	[1]	$ 747	$ 274,366	$ 115,520	$ 43,021	433,654
Ending balance, shares at Dec. 31, 2017	[1]	74,734,455
Net income				68,173	9,509	77,682
Member distributions to non-controlling interest holder					(4,900)	(4,900)
Dividends to shareholders				(33,631)		(33,631)
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

[1] * See Note 2 for summary of adjustments.