CONSOLIDATED STATEMENTS OF EQUITY - USD ($) $ in Millions	Total	Cumulative effect of period of adoption, adjusted balance	Parent	Parent Cumulative effect of period of adoption, adjusted balance	Preferred Stock and Additional Paid-In Capital	Common Stock	Additional Paid-in Capital	Treasury Stock	Retained Earnings	Retained Earnings Cumulative effect of period of adoption, adjusted balance	AOCI Attributable to Parent	Non-controlling Interest
Beginning of year at Dec. 31, 2016									$ 11,360		$ (920)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other comprehensive income (loss)	$ 811										792
End of year at Dec. 31, 2017	16,411		$ 13,314						12,138		(128)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other comprehensive income (loss)	(1,169)										(1,184)
End of year at Dec. 31, 2018	15,368		13,802		$ 0	$ 5	$ 1,908	$ (640)	13,937		(1,408)	$ 1,566
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other comprehensive income (loss)	884										885
Other	(7)
End of year at Mar. 31, 2019	14,591		13,052				1,882		12,922		(523)
Beginning of year at Dec. 31, 2018	15,368		13,802		0	5	1,908	(640)	13,937		(1,408)	1,566
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other comprehensive income (loss)	2,195										2,197
Other							(16)
End of year at Jun. 30, 2019	16,217		14,672		0	5	1,901	(1,232)	13,209		789	1,545
Beginning of year at Dec. 31, 2018	15,368		13,802		0	5	1,908	(640)	13,937		(1,408)	1,566
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock compensation	13		(3)				(11)	8				16
Purchase of treasury stock	(637)		(637)					(637)
Reissuance of treasury stock	(1)		(1)						(1)
Retirement of common stock	(142)		(142)						(142)
Repurchase of AB Holding units	(30)											(30)
Dividends paid to noncontrolling interest	(186)											(186)
Dividends	(215)		(215)						(215)
Net income (loss)	(643)		(818)						(818)			175
Other comprehensive income (loss)	2,947		2,954								2,954	(7)
Other	8											8
End of year at Sep. 30, 2019	16,482		14,940		0	5	1,897	(1,269)	12,761		1,546	1,542
Beginning of year at Dec. 31, 2018	15,368		13,802		0	5	1,908	(640)	13,937		(1,408)	1,566
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other comprehensive income (loss)	2,248										2,252
End of year at Dec. 31, 2019	15,047	$ (30)	13,456	$ (30)	775	5	1,920	(1,832)	11,744	$ (30)	844	1,591
Beginning of year at Mar. 31, 2019	14,591		13,052				1,882		12,922		(523)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other comprehensive income (loss)	1,311										1,312
Other							(9)
End of year at Jun. 30, 2019	16,217		14,672		0	5	1,901	(1,232)	13,209		789	1,545
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock compensation	(10)		(14)				(20)	6				4
Purchase of treasury stock	(43)		(43)					(43)
Reissuance of treasury stock	(1)		(1)						(1)
Retirement of common stock	1		1						1
Repurchase of AB Holding units	(9)											(9)
Dividends paid to noncontrolling interest	(62)											(62)
Dividends	(74)		(74)						(74)
Net income (loss)	(313)		(374)						(374)			61
Other comprehensive income (loss)	752		757								757	(5)
Other	24		16				16					8
End of year at Sep. 30, 2019	16,482		14,940		0	5	1,897	(1,269)	12,761		1,546	1,542
Beginning of year at Dec. 31, 2019	15,047	(30)	13,456	(30)	775	5	1,920	(1,832)	11,744	(30)	844	1,591
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other comprehensive income (loss)	1,437
End of year at Mar. 31, 2020	21,535		19,981						17,007
Beginning of year at Dec. 31, 2019	15,047	(30)	13,456	(30)	775	5	1,920	(1,832)	11,744	(30)	844	1,591
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other comprehensive income (loss)	3,079
End of year at Jun. 30, 2020	19,038		17,498		775	5	1,938	(2,047)	12,899		3,928	1,540
Beginning of year at Dec. 31, 2019	15,047	$ (30)	13,456	$ (30)	775	5	1,920	(1,832)	11,744	$ (30)	844	1,591
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock compensation	67		59				44	15				8
Purchase of treasury stock	(330)		(330)					(330)
Reissuance of treasury stock	(16)		(16)						(16)
Repurchase of AB Holding units	(50)		(31)				(31)					(19)
Dividends paid to noncontrolling interest	(230)											(230)
Dividends	(222)		(222)						(222)
Dividends on preferred stock	(34)		(34)						(34)
Issuance of preferred stock	494		494		494
Net income (loss)	791		590						590			201
Other comprehensive income (loss)	3,345		3,344								3,344	1
Other	20		20				20
End of year at Sep. 30, 2020	$ 18,852		17,300		1,269	5	1,953	(2,147)	12,032		4,188	1,552
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting standards update [extensible list]	us-gaap:AccountingStandardsUpdate201613Member
Beginning of year at Mar. 31, 2020	$ 21,535		19,981						17,007
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other comprehensive income (loss)	1,642
End of year at Jun. 30, 2020	19,038		17,498		775	5	1,938	(2,047)	12,899		3,928	1,540
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock compensation	18		15				15					3
Purchase of treasury stock	(100)		(100)					(100)
Reissuance of treasury stock	(1)		(1)						(1)
Repurchase of AB Holding units	(2)											(2)
Dividends paid to noncontrolling interest	(68)											(68)
Dividends	(76)		(76)						(76)
Dividends on preferred stock	(11)		(11)						(11)
Issuance of preferred stock	494		494		494
Net income (loss)	(706)		(779)						(779)			73
Other comprehensive income (loss)	266		260								260	6
Other	0		0				0
End of year at Sep. 30, 2020	$ 18,852		$ 17,300		$ 1,269	$ 5	$ 1,953	$ (2,147)	$ 12,032		$ 4,188	$ 1,552