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 Interests [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				47,685	5,924	53,609
Dividends to shareholders				(22,420)		(22,420)
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

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