Derivative Instruments and Hedging Activities (Schedule of Outstanding Oil and Natural Gas Derivative Contracts) (Details) - Forecast - Not Designated as Hedging Instrument	12 Months Ended
	Dec. 31, 2019 MMBTU $ / MMBTU MBbls	Dec. 31, 2018 MMBTU $ / MMBTU MBbls
Oil | Collar contracts (two-way collars)
Derivative [Line Items]
Total volume (MBbls) | MBbls	0	365,000
Oil | Collar contracts (two-way collars) | Call option | Short
Derivative [Line Items]
Strike price (in dollars per share)	0	60.50
Oil | Collar contracts (two-way collars) | Put option | Long
Derivative [Line Items]
Strike price (in dollars per share)	0	50
Oil | Collar contracts combined with short puts (three-way collars)
Derivative [Line Items]
Total volume (MBbls) | MBbls	730,000	3,468,000
Oil | Collar contracts combined with short puts (three-way collars) | Call option | Short
Derivative [Line Items]
Strike price (in dollars per share)	58.50	60.86
Oil | Collar contracts combined with short puts (three-way collars) | Put option | Short
Derivative [Line Items]
Strike price (in dollars per share)	40	39.21
Oil | Collar contracts combined with short puts (three-way collars) | Put option | Long
Derivative [Line Items]
Strike price (in dollars per share)	50	48.95
Oil | Collar contracts combined with short puts (WTI, three-way collars), Subsequent contracts
Derivative [Line Items]
Total volume (MBbls) | MBbls	1,095,000	0
Oil | Collar contracts combined with short puts (WTI, three-way collars), Subsequent contracts | Call option | Short
Derivative [Line Items]
Strike price (in dollars per share)	65	0
Oil | Collar contracts combined with short puts (WTI, three-way collars), Subsequent contracts | Put option | Short
Derivative [Line Items]
Strike price (in dollars per share)	45	0
Oil | Collar contracts combined with short puts (WTI, three-way collars), Subsequent contracts | Put option | Long
Derivative [Line Items]
Strike price (in dollars per share)	55	0
Oil | Swap contracts
Derivative [Line Items]
Total volume (MBbls) | MBbls	0	2,009,000
Average swap price (in dollars per share)	0.00	51.78
Oil | Swap contracts | Oil contracts (Midland basis differential)
Derivative [Line Items]
Total volume (MBbls) | MBbls	0	5,289,000
Average swap price (in dollars per share)	0.00	0.86
Natural gas | Collar contracts (Henry Hub, two-way collars)
Derivative [Line Items]
Total volume (BBtu) | MMBTU	0	720,000
Natural gas | Collar contracts (Henry Hub, two-way collars) | Call option | Short
Derivative [Line Items]
Strike price (in dollars per share)	0	3.84
Natural gas | Collar contracts (Henry Hub, two-way collars) | Put option | Long
Derivative [Line Items]
Strike price (in dollars per share)	0	3.40
Natural gas | Swap contracts | Swap contracts (Henry Hub), Subsequent contracts
Derivative [Line Items]
Strike price (in dollars per share)	0	2.95
Total volume (BBtu) | MMBTU	0	3,366,000