CONDENSED CONSOLIDATED STATEMENTS OF EQUITY - USD ($) shares in Millions, $ in Millions	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Unearned ESOP Compensation [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings [Member]	Total Common Shareholders' Equity Parent [Member]	Noncontrolling Interest [Member]
Beginning Balance (in shares) at Dec. 31, 2014		443
Beginning Balance at Dec. 31, 2014	$ 20,168	$ 4	$ 7,193	$ (14)	$ (40)	$ 12,773	$ 19,916	$ 252
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	650					650	650
Issuances of common stock, net of issuance cost of less than $1			13	1			14
Exercise of stock options and other incentive plan activity (in shares)		1
Exercise of stock options and other incentive plan activity			2				2
Dividends on common stock						(341)	(341)
Earned compensation under ESOP			10	1			11
Other comprehensive loss	(36)				(33)		(33)	(3)
Sale of NEER assets to NEP			16				16	(11)
Distributions to noncontrolling interests								(4)
Other								(5)
Ending Balance (in shares) at Mar. 31, 2015		444
Ending Balance at Mar. 31, 2015	$ 20,464	$ 4	7,234	(12)	(73)	13,082	20,235	229
Beginning Balance (in shares) at Dec. 31, 2015	461	461
Beginning Balance at Dec. 31, 2015	$ 23,112	$ 5	8,597	(1)	(167)	14,140	22,574	538
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	637					636	636	1
Issuances of common stock, net of issuance cost of less than $1			8				8
Exercise of stock options and other incentive plan activity			3				3
Dividends on common stock						(401)	(401)
Earned compensation under ESOP			10	1			11
Other comprehensive loss	$ 40				54		54	(14)
Sale of NEER assets to NEP			27				27	198
Distributions to noncontrolling interests								(9)
Other								4
Ending Balance (in shares) at Mar. 31, 2016	461	461
Ending Balance at Mar. 31, 2016	$ 23,630	$ 5	$ 8,645	$ 0	$ (113)	$ 14,375	$ 22,912	$ 718