Equity - Common Stock (Details) $ in Millions			3 Months Ended			9 Months Ended
	Apr. 14, 2020	Apr. 13, 2020	Sep. 30, 2020 USD ($) shares	Jun. 30, 2020 USD ($) shares	Sep. 30, 2019 USD ($) shares	Sep. 30, 2020 USD ($) shares	Sep. 30, 2019 USD ($) shares
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock, shares issued, beginning balance (shares)			9,780,000		8,172,000	9,772,793	4,568,000
Restricted stock issuances (net of forfeitures and cancellations) (shares)			0		2,000	7,000	19,000
Common stock, shares issued, ending balance (shares)			9,780,371	9,780,000	9,771,000	9,780,371	9,771,000
Loss on exchange of preferred stock | $			$ 0	$ 17	$ 17	$ 0	$ 17
COMMON STOCK
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock split, conversion ratio	0.005	0.005
PREFERRED STOCK
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock issued, exchanged (in shares)			0		40,000	0	40,000
PREFERRED STOCK | 5.75% (A)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock issued, exchanged (in shares)				40,000
Interest rate, stated percentage				5.75%
Exchange of convertible notes for shares of common stock | COMMON STOCK
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock issued, exchanged (in shares)			0		367,000	0	367,000
Exchange of senior notes for shares of common stock | COMMON STOCK
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock issued, exchanged (in shares)			0		1,178,000	0	1,178,000
Exchange of preferred stock for shares of common stock | COMMON STOCK
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock issued, exchanged (in shares)			0	51,839	52,000	0	52,000
Wildhorse Resource Development Corporation
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common shares issued for WildHorse Merger (shares)			0		0	0	3,587,000