Derivative Instruments and Hedging Activities (Schedule of Outstanding Oil and Natural Gas Derivative Contracts) (Details) - Forecast - Not Designated as Hedging Instrument	9 Months Ended	12 Months Ended
	Dec. 31, 2018 MMBTU $ / MMBTU MBbls	Dec. 31, 2019 MMBTU $ / MMBTU MBbls
Oil | Swap contracts
Derivative [Line Items]
Total volume (MBbls) | MBbls	1,559,000	0
Average swap price (in dollars per share)	51.88	0.00
Oil | Collar contracts (two-way collars)
Derivative [Line Items]
Total volume (MBbls) | MBbls	275,000	0
Oil | Collar contracts (two-way collars) | Call option | Short
Derivative [Line Items]
Strike price (in dollars per share)	60.50	0
Oil | Collar contracts (two-way collars) | Put option | Long
Derivative [Line Items]
Strike price (in dollars per share)	50	0
Oil | Collar contracts combined with short puts (three-way collars)
Derivative [Line Items]
Total volume (MBbls) | MBbls	2,612,000	2,739,000
Oil | Collar contracts combined with short puts (three-way collars) | Call option | Short
Derivative [Line Items]
Strike price (in dollars per share)	60.86	62.96
Oil | Collar contracts combined with short puts (three-way collars) | Put option | Short
Derivative [Line Items]
Strike price (in dollars per share)	39.21	43.67
Oil | Collar contracts combined with short puts (three-way collars) | Put option | Long
Derivative [Line Items]
Strike price (in dollars per share)	48.95	53.67
Oil | Oil contracts (Midland basis differential) | Swap contracts
Derivative [Line Items]
Total volume (MBbls) | MBbls	3,895,000	0
Average swap price (in dollars per share)	0.86	0.00
Natural gas | Swap contracts | Swap contracts
Derivative [Line Items]
Total volume (BBtu) | MMBTU	4,125,000	0
Strike price (in dollars per share)	2.91	0