Supplemental Gas Data Proved Undeveloped Reserves (Details) bbl in Thousands, Mcfe in Thousands, Mcf in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) Mcfe Mcf bbl	Dec. 31, 2017 USD ($) Mcfe Mcf bbl	Dec. 31, 2016 USD ($) Mcfe Mcf bbl
Proved Developed and Undeveloped Reserve (Energy) [Roll Forward]
Beginning balance (energy)	7,581,612	6,251,648	5,642,989
Revisions (energy)	320,925	(232,321)	(99,849)
Price changes (energy)	28,315	181,470	(190,009)
Extensions and Discoveries (energy)	960,808	1,887,153	720,146
Production (MMcfe)	(507,104)	(407,166)	(394,387)
Sales of Reserves In-Place (energy)	(825,196)	(99,172)	(870,884)
Acquisition of reserves in place	321,975		1,443,642
Ending balance (energy)	7,881,335	7,581,612	6,251,648
Proved developed resources (energy)	4,494,878	4,409,065	3,683,302
Proved undeveloped resources (energy)	3,386,457	3,172,547	2,568,346
Downward revision for wells removed from development plans (energy)			255,000
Downward revision related to economics for producing properties (energy)	113,000
Offset due to improved analog performance (energy)			268,000
Downward revision due to PUD removal (energy)		458,000
Upward revision from increased performance through optimization (energy)	472,000
Downward revision due to plan changes (energy)	151,000
Capital spent related to undeveloped reserves transferred to developed | $	$ 1,116,397,000	$ 632,846,000	$ 172,739,000
Reserves reported for more than five years	281,696
Proved Undeveloped
Proved Developed and Undeveloped Reserve (Energy) [Roll Forward]
Capital spent related to undeveloped reserves transferred to developed | $	$ 480,003
Proved Undeveloped
Proved Developed and Undeveloped Reserve (Energy) [Roll Forward]
Beginning balance (energy)	3,172,547
Undeveloped reserves transferred to developed	(1,037,727)
Extensions and Discoveries (energy)	921,488
Sales of Reserves In-Place (energy)	(27,741)
Acquisition of reserves in place	321,975
Ending balance (energy)	3,386,457	3,172,547
Proved Undeveloped | Price Revisions
Proved Developed and Undeveloped Reserve (Energy) [Roll Forward]
Revisions (energy)	(2,489)
Proved Undeveloped | Revisions Due to Plan Changes
Proved Developed and Undeveloped Reserve (Energy) [Roll Forward]
Revisions (energy)	(151,550)
Proved Undeveloped | Revisions Due to Changes Due to Well Performance
Proved Developed and Undeveloped Reserve (Energy) [Roll Forward]
Revisions (energy)	189,954
Natural Gas
Proved Developed and Undeveloped Reserves [Roll Forward]
Beginning balance (volume) | Mcf	7,121,758	5,828,399	5,060,215
Revisions (volume) | Mcf	313,091	(202,735)	11,559
Price Changes (volume) | Mcf	28,100	173,738	(179,914)
Extension and Discoveries (volume) | Mcf	839,268	1,769,029
Production (volume) | Mcf	(468,228)	(364,893)	(348,753)
Purchases of Reserves In-Place (volume) | Mcf	317,437		1,352,759
Sales of Reserves In-Place (volume) | Mcf	(715,088)	(81,780)	(711,155)
Ending balance (volume) | Mcf	7,436,338	7,121,758	5,828,399
Proved Developed and Undeveloped Reserve (Energy) [Roll Forward]
Proved developed resources (volume) | Mcf	4,242,579	4,051,526	3,478,464
Proved undeveloped resources (volume) | Mcf	3,193,759	3,070,232	2,349,934
Natural Gas | Revisions Due to Changes Due to Well Performance
Proved Developed and Undeveloped Reserves [Roll Forward]
Extension and Discoveries (volume) | Mcf			643,688
NGLs
Proved Developed and Undeveloped Reserves [Roll Forward]
Beginning balance (volume) | bbl	71,691,000	60,532,000	86,212,000
Revisions (volume) | bbl	441,000	1,162,000	(19,078,000)
Price Changes (volume) | bbl	32,000	1,188,000	(1,647,000)
Extension and Discoveries (volume) | bbl	16,247,000	17,887,000
Production (volume) | bbl	(6,011,000)	(6,456,000)	(6,710,000)
Purchases of Reserves In-Place (volume) | bbl	756,000		13,177,000
Sales of Reserves In-Place (volume) | bbl	(17,252,000)	(2,622,000)	(22,382,000)
Ending balance (volume) | bbl	65,904,000	71,691,000	60,532,000
Proved Developed and Undeveloped Reserve (Energy) [Roll Forward]
Proved developed resources (volume) | bbl	40,180,000	56,022,000	30,666,000
Proved undeveloped resources (volume) | bbl	25,724,000	15,669,000	29,866,000
NGLs | Revisions Due to Changes Due to Well Performance
Proved Developed and Undeveloped Reserves [Roll Forward]
Extension and Discoveries (volume) | bbl			10,960,000
Condensate & Crude Oil
Proved Developed and Undeveloped Reserves [Roll Forward]
Beginning balance (volume) | bbl	4,950,000	10,009,000	10,916,000
Revisions (volume) | bbl	865,000	(5,834,000)	510,000
Price Changes (volume) | bbl	4,000	(159,000)	(34,000)
Extension and Discoveries (volume) | bbl	4,010,000	1,800,000
Production (volume) | bbl	(468,000)	(589,000)	(896,000)
Purchases of Reserves In-Place (volume) | bbl	0		1,970,000
Sales of Reserves In-Place (volume) | bbl	(1,100,000)	(277,000)	(4,240,000)
Ending balance (volume) | bbl	8,261,000	4,950,000	10,009,000
Proved Developed and Undeveloped Reserve (Energy) [Roll Forward]
Proved developed resources (volume) | bbl	1,870,000	3,567,000	3,474,000
Proved undeveloped resources (volume) | bbl	6,391,000	1,383,000	6,536,000
Condensate & Crude Oil | Revisions Due to Changes Due to Well Performance
Proved Developed and Undeveloped Reserves [Roll Forward]
Extension and Discoveries (volume) | bbl			1,783,000