Supplemental Oil and Gas Disclosures (Unaudited), Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves (Details) $ in Thousands		12 Months Ended
		Dec. 31, 2016 USD ($) Boe location $ / bbl $ / MMBTU	Dec. 31, 2015 USD ($) Boe location $ / bbl $ / MMBTU	Dec. 31, 2014 USD ($) Boe $ / bbl $ / MMBTU	Dec. 31, 2016 USD ($) Boe location	Dec. 31, 2015 USD ($) Boe	Dec. 31, 2014 USD ($) Boe
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Line Items]
Period for standardize measure of discounted future net cash flows		12 months
Number of years of experience of Evaluator		38 years
Discount rate (in hundredths)		10.00%
Future net cash inflows after income taxes discounted at 10% annual discount rate to arrive at Standardized Measure [Abstract]
Future cash inflows | $					$ 999,716	$ 1,241,334	$ 2,988,464
Future production costs | $					(357,917)	(438,784)	(921,977)
Future development costs | $					(267,836)	(338,316)	(557,782)
Future income tax expense | $					0	0	(373,095)
Future net cash flows | $					373,963	464,234	1,135,610
Discount | $					(213,363)	(266,983)	(623,053)
Standardized Measure of discounted future net cash relating to proved reserves | $		$ 197,251	$ 512,557	$ 340,985	$ 160,600	$ 197,251	$ 512,557
Analysis of the changes in Standardized Measure [Roll Forward]
Standardized Measure, beginning of year | $		197,251	512,557	340,985
Sales and transfers of oil and gas produced, net of production costs | $		32,834	37,249	96,364
Net change in prices and development and production costs from prior year | $		(58,425)	(488,160)	150,504
Extensions, discoveries, and improved recovery, less related costs | $		5,531	63,341	147,275
Sales of minerals in place | $		(4,433)	(197)	(15,042)
Revisions of previous quantity estimates | $		12,317	(49,602)	74,390
Change in timing and other | $		21,468	20,419	(82,653)
Change in future income tax expense | $		0	124,886	(40,636)
Accretion of discount | $		19,725	51,256	34,098
Standardized Measure, end of year | $		$ 160,600	$ 197,251	$ 512,557
Oil and gas prices considered in standardized measure of discounted future net cash flows [Abstract]
Oil (in dollars per Bbl) | $ / bbl	[1]	42.74	50.12	95.28
Gas (in dollars per MMbtu) | $ / MMBTU	[2]	2.50	2.63	4.35
Oil (in dollars per Bbl) | $ / bbl	[3]	35.54	41.25	87.11
Gas (in dollars per MMBtu) | $ / MMBTU	[4]	1.41	2.36	5.15
NGL's (in dollars per Bbl) | $ / bbl	[5]	5.17	10.52	37.92
Porcupine Field, Campbell County, WY [Member]
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Line Items]
Proved undeveloped locations | location					2
Oil Equivalents [Member]
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Line Items]
Proved Developed and Undeveloped Reserves, Sales of Minerals in Place, Energy		1,232,000	43,000	1,223,000
Proved Developed and Undeveloped Reserves, Production, Energy		2,262,000	2,181,000	2,088,000
Proved Developed and Undeveloped Reserves, Production, Net, Energy		2,262,000,000
Proved Developed and Undeveloped Locations Dropped Due to Lack of Economic Viability | location			48
Proved Undeveloped Reserve (Energy)					29,639,000	25,996,000	24,459,000
Proved Developed and Undeveloped Reserves (Energy), Revisions of Previous Estimates Due to Lack of Economic Viability			7,900,000
Proved Developed and Undeveloped Reserves, Production, Energy		3,424,000	(11,324,000)	4,950,000
Proved undeveloped locations dropped due to lack of economic viability | location			42
Proved developed and undeveloped reserves (energy), revisions of previous estimates due to shortened economic life calculations			614,000
Extensions and discoveries		1,537,000	14,332,000	9,797,000
Proved Developed Reserves					15,018,000	17,194,000	17,948,000
Oil Equivalents [Member] | Texas - Montoya [Member]
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Line Items]
Proved Undeveloped Reserves (Energy)					6.5
Gas and Oil Area, Undeveloped, Additional Locations | location		6
Oil Equivalents [Member] | North Dakota - Three Forks [Member]
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Line Items]
Proved Undeveloped Reserves (Energy)					4,900,000,000
Gas and Oil Area, Undeveloped, Additional Locations | location		20
Oil Equivalents [Member] | Porcupine Field, Campbell County, WY [Member]
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Line Items]
Proved Developed and Undeveloped Reserves, Production, Energy		670,000
Proved developed and undeveloped reserves (energy), revisions of previous estimates due to shortened economic life calculations		2,271,000
Oil Equivalents [Member] | Ward County, TX [Member]
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Line Items]
Proved Undeveloped Locations Added | location		5
Proved Undeveloped Reserve (Energy)					805,000
Proved Developed Reserves					449,000
Oil Equivalents [Member] | Atascosa County, TX [Member]
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Line Items]
Proved Developed Reserves					265,000,000
Oil Equivalents [Member] | McKenzie County, ND [Member]
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Line Items]
Proved Undeveloped Reserve (Energy)					18,000
Oil Equivalents [Member] | San Patricio County, TX and Converse County, WY [Member]
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Line Items]
Proved Developed and Undeveloped Reserves, Sales of Minerals in Place, Energy		1,232,000,000
Oil Equivalents [Member] | South Texas Eagle Ford Locations [Member]
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Line Items]
Proved Developed and Undeveloped Reserves (Energy), Revisions of Previous Estimates Due to Lack of Economic Viability			7,717,000
Proved undeveloped locations dropped due to lack of economic viability | location			38
Oil Equivalents [Member] | North Dakota - Bakken and Three Forks [Member]
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Line Items]
Proved Undeveloped Reserves (Energy)					1,600,000,000
Proved developed and undeveloped reserves (energy), revisions of previous estimates due to shortened economic life calculations			1,800,000,000
Proved Developed and Undeveloped Reserves (Energy), Revisions of Previous Estimates, Increase Due To Better Than Anticipated Production			600,000
Proved developed and undeveloped reserves (energy), revisions of previous estimates due to lower than anticipated performance			1,600,000,000
Oil Equivalents [Member] | North Dakota - Bakken and Three Forks [Member]
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Line Items]
Proved Developed and Undeveloped Reserves, Production, Energy		1,360,000

[1] The quoted oil price for the year ended December 31 of each year, 2014, 2015 and 2016 is the 12-month unweighted average first-day-of-the-month West Texas Intermediate spot price for each month of 2014, 2015 and 2016.

[2] The quoted gas price for the year ended December 31, 2014, 2015 and 2016 is the 12-month unweighted average first-day-of-the-month Henry Hub spot price for each month of 2014, 2015 and 2016.

[3] The oil price is the realized price at the wellhead as of December 31 of each year after the appropriate differentials have been applied.

[4] The gas price is the realized price at the wellhead as of December 31 of each year after the appropriate differentials have been applied.

[5] The NGL price is the realized price as of December 31 of each year after the appropriate differentials have been applied.