Capital Adequacy (Tables)
 3 Months Ended
Mar. 31, 2015
Regulatory Capital Requirements [Abstract]  
Schedule of Minimum and Well-Capitalized Requirements
The following table shows the actual capital amounts and ratios of the Company and Discover Bank and comparisons of each to the regulatory minimum and “well-capitalized” requirements (dollars in millions): 
 
Actual
 
Minimum Capital
Requirements
 
Capital Requirements
To Be Classified as
Well-Capitalized
 
Amount
 
Ratio
 
Amount
 
Ratio
 
Amount
 
Ratio
At March 31, 2015(1)
 
 
 
 
 
 
 
 
 
 
 
Total capital (to risk-weighted assets)
 
 
 
 
 
 
 
 
 
 
 
Discover Financial Services
$
12,471

 
17.6
%
 
$
5,669

 
≥8.0%
 
$
7,086

 
≥10.0%
Discover Bank
$
11,670

 
16.7
%
 
$
5,595

 
≥8.0%
 
$
6,993

 
≥10.0%
Tier 1 capital (to risk-weighted assets)
 
 
 
 
 
 
 
 
 
 
 
Discover Financial Services
$
11,057

 
15.6
%
 
$
4,252

 
≥6.0%
 
$
5,669

 
≥8.0%
Discover Bank
$
9,627

 
13.8
%
 
$
4,196

 
≥6.0%
 
$
5,595

 
≥8.0%
Tier 1 capital (to average assets)
 
 
 
 
 
 
 
 
 
 
 
Discover Financial Services
$
11,057

 
13.3
%
 
$
3,329

 
≥4.0%
 
$
4,162

 
≥5.0%
Discover Bank
$
9,627

 
11.7
%
 
$
3,286

 
≥4.0%
 
$
4,107

 
≥5.0%
CET1 capital (to risk-weighted assets) (Basel III transition)
 
 
 
 
 
 
 
 
 
 
 
Discover Financial Services
$
10,497

 
14.8
%
 
$
3,189

 
≥4.5%
 
$
4,606

 
≥6.5%
Discover Bank
$
9,627

 
13.8
%
 
$
3,147

 
≥4.5%
 
$
4,546

 
≥6.5%
CET1 capital (to risk-weighted assets) (Basel III fully phased-in)(2)
 
 
 
 
 
 
 
 
 
 
 
Discover Financial Services
$
10,410

 
14.7
%
 
$
3,184

 
≥4.5%
 
$
4,599

 
≥6.5%
Discover Bank
$
9,623

 
13.8
%
 
$
3,147

 
≥4.5%
 
$
4,545

 
≥6.5%
 
 
 
 
 
 
 
 
 
 
 
 
At December 31, 2014(1)
 
 
 
 
 
 
 
 
 
 
 
Total capital (to risk-weighted assets)
 
 
 
 
 
 
 
 
 
 
 
Discover Financial Services
$
12,418

 
17.0
%
 
$
5,831

 
≥8.0%
 
$
7,289

 
≥10.0%
Discover Bank
$
11,040

 
15.3
%
 
$
5,767

 
≥8.0%
 
$
7,209

 
≥10.0%
Tier 1 capital (to risk-weighted assets)
 
 
 
 
 
 
 
 
 
 
 
Discover Financial Services
$
10,839

 
14.9
%
 
$
2,916

 
≥4.0%
 
$
4,373

 
≥6.0%
Discover Bank
$
9,470

 
13.1
%
 
$
2,884

 
≥4.0%
 
$
4,326

 
≥6.0%
Tier 1 capital (to average assets)
 
 
 
 
 
 
 
 
 
 
 
Discover Financial Services
$
10,839

 
13.2
%
 
$
3,288

 
≥4.0%
 
$
4,111

 
≥5.0%
Discover Bank
$
9,470

 
11.7
%
 
$
3,252

 
≥4.0%
 
$
4,066

 
≥5.0%
CET1 capital (to risk-weighted assets) (Basel III transition)
 
 
 
 
 
 
 
 
 
 
 
Discover Financial Services
N/A

 
N/A

 
N/A

 
N/A
 
N/A

 
N/A
Discover Bank
N/A

 
N/A

 
N/A

 
N/A
 
N/A

 
N/A
CET1 capital (to risk-weighted assets) (Basel III fully phased-in)(2)
 
 
 
 
 
 
 
 
 
 
 
Discover Financial Services
$
10,305

 
14.1
%
 
$
3,299

 
≥4.5%
 
$
4,765

 
≥6.5%
Discover Bank
N/A

 
N/A

 
N/A

 
N/A
 
N/A

 
N/A
 
 
 
 
 
 
 
 
 
 
 
 
(1)
As of January 1, 2015, actual capital amounts and ratios are calculated under Basel III rules subject to transition provisions. The Company reported under Basel I at December 31, 2014.
(2)
CET1 (Basel III fully phased-in) is calculated using Basel III fully phased-in CET1 capital, a non-GAAP measure. The Company believes that the CET1 capital ratio based on fully phased-in Basel III rules is an important complement to the existing capital ratios and for comparability to other financial institutions. For the corresponding reconciliation of CET1 capital to risk-weighted assets calculated under fully phased-in Basel III rules to CET1 capital and risk-weighted assets calculated under Basel III transition rules see "Management's Discussion and Analysis of Financial Conditions and Results of Operations — Liquidity and Capital Resources — Capital".