Derivative Financial Instruments (Outstanding Commodity Derivative Contracts) (Detail) - Minimum [Member]		3 Months Ended											12 Months Ended
		Dec. 31, 2019 bbl $ / bbl	Sep. 30, 2019 bbl $ / bbl	Jun. 30, 2019 bbl $ / bbl	Mar. 31, 2019 bbl $ / bbl	Dec. 31, 2018 MMBTU bbl $ / bbl $ / MMBTU	Sep. 30, 2018 MMBTU bbl $ / bbl $ / MMBTU	Jun. 30, 2018 MMBTU bbl $ / bbl $ / MMBTU	Mar. 31, 2018 MMBTU bbl $ / bbl $ / MMBTU	Dec. 31, 2017 MMBTU bbl $ / bbl $ / MMBTU	Sep. 30, 2017 MMBTU bbl $ / bbl $ / MMBTU	Jun. 30, 2017 MMBTU bbl $ / bbl $ / MMBTU	Dec. 31, 2019 bbl $ / bbl	Dec. 31, 2018 MMBTU bbl $ / bbl $ / MMBTU	Dec. 31, 2017 MMBTU bbl $ / bbl $ / MMBTU
Oil Swaps [Member]
Derivative [Line Items]
Volume - Current Year | bbl	[1]									6,333,080	6,898,370	7,708,480			20,939,930
Price - Current Year | $ / bbl	[1]									52.04	51.87	57.22			53.89
Volume - Year One | bbl	[1]					4,941,007	5,204,318	5,516,170	5,875,629					21,537,124
Price - Year One | $ / bbl	[1]					51.59	51.75	51.93	52.11					51.86
Volume - Year Two | bbl	[1]	2,083,000	2,163,000	2,253,000	2,355,000								8,854,000
Price - Year Two | $ / bbl	[1]	55.16	55.14	55.11	55.15								55.14
Oil Basis Swaps [Member]
Derivative [Line Items]
Volume - Current Year | bbl	[2]									5,290,000	5,290,000	6,141,500			16,721,500
Price - Current Year | $ / bbl	[2]									(0.49)	(0.49)	(1.03)			(0.69)
Volume - Year One | bbl	[2]					3,956,000	3,956,000	3,913,000	3,870,000					15,695,000
Price - Year One | $ / bbl	[2]					(1)	(1)	(1)	(1)					(1)
Natural Gas Swap [Member]
Derivative [Line Items]
Volume - Current Year | MMBTU	[3]									14,043,000	14,665,441	14,814,642			43,523,083
Price - Current Year | $ / MMBTU	[3]									3.09	3.1	3.08			3.09
Volume - Year One | MMBTU	[3]					8,064,000	8,249,000	8,401,000	8,656,000					33,370,000
Price - Year One | $ / MMBTU	[3]					3.03	3.04	3.04	3.04					3.04

[1] The index prices for the oil price swaps are based on the New York Mercantile Exchange (“NYMEX”) – West Texas Intermediate (“WTI”) monthly average futures price.

[2] The basis differential price is between Midland – WTI and Cushing – WTI.

[3] The index prices for the natural gas price swaps are based on the NYMEX – Henry Hub last trading day futures price.