Consolidated Statements 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				20,975	2,607	$ 23,582
Dividends to shareholder				(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

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