Condensed Consolidated Statements of Equity - USD ($) $ in Millions	Total	Preferred Stock	Common stock	Additional paid-in capital	Retained earnings	Accumulated other comprehensive income (loss)	Parent	Noncontrolling interest	Preferred Stock	Preferred Stock Additional paid-in capital	Preferred Stock Parent	Common stock	Common stock Additional paid-in capital	Common stock Parent	Cumulative Effect, Period of Adoption, Adjustment	Cumulative Effect, Period of Adoption, Adjustment Retained earnings	Cumulative Effect, Period of Adoption, Adjustment Accumulated other comprehensive income (loss)	Cumulative Effect, Period of Adoption, Adjustment Parent	Cumulative Effect, Period of Adoption, Adjustment Noncontrolling interest
Beginning Balance at Dec. 31, 2018	$ 8,276	$ 0	$ 0	$ 3,462	$ 5,286	$ (472)	$ 8,276	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,721				1,721		1,721	0
Other comprehensive income (loss)	2,914					2,914	2,914
Issuance of shares, net of expenses									$ 1,172	$ 1,172	$ 1,172	$ 4	$ 4	$ 4
Stock-based compensation	23			23			23
Retirement or repurchase of shares	(548)			(226)	(322)		(548)
Dividends, Preferred Stock	(17)				(17)		(17)
Ending Balance at Sep. 30, 2019	13,545	0	0	4,435	6,668	2,442	13,545	0
Beginning Balance at Jun. 30, 2019	12,365	0	0	4,144	6,461	1,760	12,365	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	293				293		293	0
Other comprehensive income (loss)	682					682	682	0
Issuance of shares, net of expenses									333	333	333	2	2	2
Stock-based compensation	8			8			8
Retirement or repurchase of shares	(121)			(52)	(69)		(121)
Dividends, Preferred Stock	(17)				(17)		(17)
Ending Balance at Sep. 30, 2019	13,545	0	0	4,435	6,668	2,442	13,545	0
Beginning Balance at Dec. 31, 2019	14,141	0	0	4,171	6,939	2,281	13,391	750							$ (125)	$ (117)	$ (6)	$ (123)	$ (2)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	599				448		448	151
Other comprehensive income (loss)	694					613	613	81
Issuance of shares, net of expenses									$ 583	$ 583	$ 583	$ 1,509	$ 1,509	$ 1,509
Stock-based compensation	14			14			14
Retirement or repurchase of shares	(425)			(232)	(193)		(425)
Dividends, Preferred Stock	(67)				(67)		(67)
Contributions from noncontrolling interests								240							$ 240
Distributions to noncontrolling interests	(46)							(46)
Ending Balance at Sep. 30, 2020	17,117	0	0	6,045	7,010	2,888	15,943	1,174
Beginning Balance at Jun. 30, 2020	15,639	0	0	6,090	6,437	2,184	14,711	928
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	884				652		652	232
Other comprehensive income (loss)	718					704	704	14
Stock-based compensation	3			3			3
Retirement or repurchase of shares	(97)			(48)	(49)		(97)
Dividends, Preferred Stock	(30)				(30)		(30)
Ending Balance at Sep. 30, 2020	$ 17,117	$ 0	$ 0	$ 6,045	$ 7,010	$ 2,888	$ 15,943	$ 1,174