Regulatory Capital and Other Regulatory Matters (Tables)

12 Months Ended

Dec. 31, 2018

Regulatory Capital Requirements [Abstract]

Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations

The following table summarizes our capital ratios under the U.S. Basel III capital framework.

	December 31, 2018				December 31, 2017				Required minimum (a)		Well-capitalized minimum
($ in millions)	Amount		Ratio		Amount		Ratio
Capital ratios
Common Equity Tier 1 (to risk-weighted assets)
Ally Financial Inc.	$	13,397	9.14	%	$	13,237	9.53	%	4.50	%	(b)
Ally Bank	16,552		12.61		17,059		15.04		4.50		6.50	%
Tier 1 (to risk-weighted assets)
Ally Financial Inc.	$	15,831	10.80	%	$	15,628	11.25	%	6.00	%	6.00	%
Ally Bank	16,552		12.61		17,059		15.04		6.00		8.00
Total (to risk-weighted assets)
Ally Financial Inc.	$	18,046	12.31	%	$	17,974	12.94	%	8.00	%	10.00	%
Ally Bank	17,620		13.42		17,886		15.77		8.00		10.00
Tier 1 leverage (to adjusted quarterly average assets) (c)
Ally Financial Inc.	$	15,831	9.00	%	$	15,628	9.53	%	4.00	%	(b)
Ally Bank	16,552		10.69		17,059		12.87		4.00		5.00	%

(a) In addition to the minimum risk-based capital requirements for common equity Tier 1 capital, Tier 1 capital, and total capital ratios, Ally and Ally Bank were required to maintain a minimum capital conservation buffer of 1.875% and 1.25% at December 31, 2018, and December 31, 2017, respectively, which increased to 2.5% on January 1, 2019.

(b) Currently, there is no ratio component for determining whether a BHC is “well-capitalized.”

(c) Federal regulatory reporting guidelines require the calculation of adjusted quarterly average assets using a daily average methodology.

Schedule of Common Share Repurchase Activity

The following table presents information related to our common stock for each quarter since the commencement of our common-stock-repurchase programs and initiation of a quarterly cash dividend on common stock.

	Common stock repurchased during period (a)			Number of common shares outstanding		Cash dividends declared per common share (b)
($ in millions, except per share data; shares in thousands)	Approximate dollar value		Number of shares	Beginning of period	End of period
2016
Third quarter	$	159	8,298	483,753	475,470	$	0.08
Fourth quarter	167		8,745	475,470	467,000	0.08
2017
First quarter	$	169	8,097	467,000	462,193	$	0.08
Second quarter	204		10,485	462,193	452,292	0.08
Third quarter	190		8,507	452,292	443,796	0.12
Fourth quarter	190		7,033	443,796	437,054	0.12
2018
First quarter	$	185	6,473	437,054	432,691	$	0.13
Second quarter	195		7,280	432,691	425,752	0.13
Third quarter	250		9,194	425,752	416,591	0.15
Fourth quarter	309		12,121	416,591	404,900	0.15

(a) Includes shares of common stock withheld to cover income taxes owed by participants in our share-based incentive plans.

(b) On January 14, 2019, the Ally Board of Directors (the Board) declared a quarterly cash dividend of $0.17 per share on all common stock, payable on February 15, 2019. Refer to Note 31 for further information regarding this common stock dividend.