Condensed Consolidated Statements of Changes in Equity shares in Thousands, $ in Millions		USD ($) $ / shares shares		Series A Convertible Preferred Units [Member] shares	Preferred Units [Member] shares	Preferred Partner [Member] USD ($) shares	Units [Member] USD ($) shares	Limited Partners [Member] USD ($)		Accumulated Other Comprehensive Income (Loss) [Member] USD ($)	Non-controlling Interests [Member] USD ($)		Common Stock [Member] $ / shares
Beginning balance, units at Dec. 31, 2017 | shares					14,000		54,300
Beginning balance at Dec. 31, 2017		$ 2,224.0	[1]			$ 548.0		$ 1,641.0	[1]	$ 1.0	$ 34.0	[1]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Related party note receivable	[1]	29.0									29.0
Net income (loss)		(19.0)	[1]			6.0		74.0	[1]		(99.0)	[1]
Other comprehensive income (loss)	[1]	1.0									1.0
Related party distributions	[1]	(64.0)									(64.0)
Other differential membership interests activity	[1]	23.0									23.0
Changes in non-economic ownership interests	[1]	(6.0)									(6.0)
Distributions to unitholders	[2]	(28.0)	[1]			(6.0)		(22.0)	[1]
Ending balance, units at Mar. 31, 2018 | shares					14,000		54,300
Ending balance at Mar. 31, 2018		$ 3,583.0	[1]			548.0		1,702.0	[1]	1.0	1,332.0	[1]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Distributions per common unit (usd per share) | $ / shares		$ 0.4050
Beginning balance, units at Dec. 31, 2017 | shares					14,000		54,300
Beginning balance at Dec. 31, 2017		$ 2,224.0	[1]			548.0		1,641.0	[1]	1.0	34.0	[1]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	[3],[4]	383.0
Other comprehensive income (loss)	[5]	4.0
Ending balance, units at Sep. 30, 2018 | shares					14,000		56,000
Ending balance at Sep. 30, 2018		4,046.0	[1]			548.0		1,847.0	[1]	(5.0)	1,656.0	[1]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accrued preferred distributions	[4]	6.0
Beginning balance, units at Mar. 31, 2018 | shares					14,000		54,300
Beginning balance at Mar. 31, 2018		3,583.0	[1]			548.0		1,702.0	[1]	1.0	1,332.0	[1]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Related party note receivable	[1]	2.0									2.0
Net income (loss)		292.0	[1]			6.0		82.0	[1]		204.0	[1]
Other comprehensive income (loss)	[1]	(5.0)								(1.0)	(4.0)
Related party distributions	[1]	(41.0)									(41.0)
Other differential membership interests activity	[1]	(6.0)									(6.0)
Changes in non-economic ownership interests	[1]	1.0									1.0
Distributions to unitholders	[2]	(29.0)	[1]			(6.0)		(23.0)	[1]
Disposal of Canadian Holdings		107.0	[1]							2.0	105.0
Ending balance, units at Jun. 30, 2018 | shares					14,000		54,300
Ending balance at Jun. 30, 2018		$ 3,904.0	[1]			$ 548.0		1,759.0	[1]	2.0	1,595.0	[1]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Distributions per common unit (usd per share) | $ / shares		$ 0.4200
Partners' Capital Account, Distributions		$ (2.0)						(2.0)
Issuance of common units (in units) | shares	[6]				0	0	(1,700)
Issuance of common units - net	[6]	81.0						81.0
Net income (loss)		110.0	[1],[3]			$ 6.0		33.0	[1]		71.0	[1]
Other comprehensive income (loss)	[1]	8.0	[5]							(7.0)	15.0
Related party contributions		1.0									1.0
Related party distributions		(48.0)									(48.0)
Other differential membership interests activity	[1]	23.0									23.0
Changes in non-economic ownership interests	[1]	(1.0)									(1.0)
Distributions to unitholders	[2]	(30.0)	[1]			(6.0)		(24.0)	[1]
Ending balance, units at Sep. 30, 2018 | shares					14,000		56,000
Ending balance at Sep. 30, 2018		$ 4,046.0	[1]			548.0		1,847.0	[1]	(5.0)	1,656.0	[1]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Distributions per common unit (usd per share) | $ / shares		$ 0.4375
Beginning balance, units at Dec. 31, 2018 | shares		56,100			14,000		56,100
Beginning balance at Dec. 31, 2018		$ 5,538.0				548.0		1,804.0		(6.0)	3,192.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common units (in units) | shares							(100)
Issuance of common units - net		1.0						1.0
Net income (loss)		(121.0)				6.0		(22.0)			(105.0)
Other comprehensive income (loss)		(5.0)								(2.0)	(3.0)
Related party contributions		1.0									1.0
Related party distributions		(51.0)									(51.0)
Other differential membership interests activity		24.0									24.0
Changes in non-economic ownership interests		(6.0)									(6.0)
Payments to Class B noncontrolling interests investors		(5.0)									(5.0)
Distributions to unitholders	[7]	(32.0)				(6.0)		(26.0)
Other		1.0									1.0
Ending balance, units at Mar. 31, 2019 | shares					14,000		56,200
Ending balance at Mar. 31, 2019		$ 5,345.0				548.0		1,757.0		(8.0)	3,048.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Distributions per common unit (usd per share) | $ / shares													$ 0.4650
Beginning balance, units at Dec. 31, 2018 | shares		56,100			14,000		56,100
Beginning balance at Dec. 31, 2018		$ 5,538.0				548.0		1,804.0		(6.0)	3,192.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)		(488.0)
Other comprehensive income (loss)		$ (5.0)
Ending balance, units at Sep. 30, 2019 | shares		60,800			9,300		60,800
Ending balance at Sep. 30, 2019		$ 6,176.0				365.0		1,803.0		(8.0)	4,016.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accrued preferred distributions		4.0
Beginning balance, units at Mar. 31, 2019 | shares					14,000		56,200
Beginning balance at Mar. 31, 2019		5,345.0				548.0		1,757.0		(8.0)	3,048.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common units - net		1.0						1.0
Changes in non-economic ownership interests		472.0									472.0
Related party note receivable		1.0									1.0
Net income (loss)		(124.0)				6.0		(28.0)			(102.0)
Other comprehensive income (loss)		0.0
Related party contributions		11.0									11.0
Related party distributions		(56.0)									(56.0)
Other differential membership interests activity		(8.0)									(8.0)
Payments to Class B noncontrolling interests investors		(3.0)									(3.0)
Distributions to unitholders	[7]	(33.0)				(6.0)		(27.0)
Sale of Class B noncontrolling interest - net		893.0									893.0
Other		1.0						1.0
Ending balance, units at Jun. 30, 2019 | shares					14,000		56,200
Ending balance at Jun. 30, 2019		6,500.0				$ 548.0		1,704.0		(8.0)	4,256.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Distributions per common unit (usd per share) | $ / shares													0.4825
Partners' Capital Account, Contributions								20.0
Issuance of common units (in units) | shares	[6]				(4,700)	(183,000)	(4,700)
Issuance of common units - net	[6]	20.0						203.0
Changes in non-economic ownership interests		11.0						1.0			10.0
Net income (loss)		(243.0)				$ 2.0		(72.0)			(173.0)
Other comprehensive income (loss)		0.0
Related party distributions		(71.0)									(71.0)
Other differential membership interests activity		27.0									27.0
Changes in non-economic ownership interests		(6.0)									(6.0)
Payments to Class B noncontrolling interests investors		(7.0)									(7.0)
Distributions to unitholders	[7]	(33.0)				(2.0)		(31.0)
Other		$ 0.0					$ (0.1)	0.0
Ending balance, units at Sep. 30, 2019 | shares		60,800			9,300		60,800
Ending balance at Sep. 30, 2019		$ 6,176.0				$ 365.0		$ 1,803.0		$ (8.0)	$ 4,016.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Distributions per common unit (usd per share) | $ / shares													$ 0.5025
Conversion of stock, shares converted (in shares) | shares				4,670
Conversion ratio				1

[1] Prior-period financial information has been retrospectively adjusted to include the adoption of an accounting standards update related to leases.

[2] Distributions per common unit of $0.4375, $0.4200 and $0.4050 were paid during the three months ended September 30, 2018, June 30, 2018 and March 31, 2018, respectively.

[3] Prior-period financial information has been retrospectively adjusted to include the adoption of an accounting standards update related to leases.

[4] Prior-period financial information has been retrospectively adjusted to include the adoption of an accounting standards update related to leases.

[5] Prior-period financial information has been retrospectively adjusted to include the adoption of an accounting standards update related to leases.

[6] During the three months ended September 30, 2019, NEP converted approximately 4.67 million Series A convertible preferred units into NEP common units on a one-for-one basis and recognized a deferred tax asset of $20 million related to the issuance of NEP common units.

[7] Distributions per common unit of $0.5025, $0.4825 and $0.4650 were paid during the three months ended September 30, 2019, June 30, 2019 and March 31, 2019, respectively. At September 30, 2019, $4 million of preferred unit distributions were accrued and are payable in November 2019.