Supplemental Oil And Natural Gas Disclosures (Components Of Changes In Standardized Measure Of Discounted Future Net Cash Flows) (Details) - USD ($) $ in Thousands	1 Months Ended	11 Months Ended	12 Months Ended
	Feb. 08, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Components of changes in standardized measure of discounted future net cash flows
Balance at beginning of year		$ 1,179,886
Sales of oil and natural gas, net of production costs		(278,091)
Changes in sales and transfer prices, net of production costs		38,963
Revisions of previous quantity estimates		(1,120,097)
Purchases of reserves-in-place		24,376
Sales of reserves-in-place		0
Current year discoveries and extensions		684,700
Changes in estimated future development costs		(39,069)
Development costs incurred during the year		160,583
Accretion of discount		117,989
Net change in income taxes		0
Change in production rate (timing) and other		43,611
Net change		(367,035)
Balance at end of year	$ 1,179,886	812,851
Amount of proved undeveloped reserves, derecognized		250,000
Predecessor
Components of changes in standardized measure of discounted future net cash flows
Balance at beginning of year	1,105,922	$ 1,179,886	$ 558,608	$ 629,596
Sales of oil and natural gas, net of production costs	(30,391)		(202,232)	(124,610)
Changes in sales and transfer prices, net of production costs	71,334		354,900	(324,638)
Revisions of previous quantity estimates	10,887		(12,106)	(35,972)
Purchases of reserves-in-place	0		11,483	40,611
Sales of reserves-in-place	(4,807)		(20,423)	2,345
Current year discoveries and extensions	0		513,012	356,631
Changes in estimated future development costs	491		(5,869)	849
Development costs incurred during the year	0		26,317	8,363
Accretion of discount	110,592		55,861	62,960
Net change in income taxes	0		0	0
Change in production rate (timing) and other	(84,142)		(173,629)	(57,527)
Net change	73,964		547,314	(70,988)
Balance at end of year	$ 1,179,886		$ 1,105,922	$ 558,608