Investment Securities (Contractual Maturity) (Details) - USD ($)
$ in Millions |
Jun. 30, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
| Available-for-sale Securities, Maturities, Amortized Cost [Abstract] |
|
|
|
| Available-for-sale Securities, Debt Maturities, Year Two Through Five, Amortized Cost Basis |
$ 18
|
|
|
| Available-for-sale Securities, Debt Maturities, Year Two Through Five, Fair Value |
18
|
|
|
| Due after five years through ten years, amortized cost |
7
|
$ 14
|
|
| Due after ten years, amortized cost |
1,093
|
1,280
|
|
| Total, amortized cost |
1,118
|
1,294
|
|
| Available-for-sale Securities, Maturities, Fair Value [Abstract] |
|
|
|
| Due after five years through ten years, estimated fair value |
7
|
14
|
|
| Due after ten years, estimated fair value |
1,120
|
1,280
|
|
| Fair Value |
$ 1,145
|
$ 1,294
|
$ 1,672
|
| Available-for-sale Securities, Maturities, Weighted Average Yield [Abstract] |
|
|
|
| Available-For-Sale Securities, Debt Maturities, Year Two Through Five, Weighted Average Yield |
3.97%
|
|
|
| Due after five years through ten years, weighted average yield (as a percent) |
2.66%
|
4.47%
|
|
| Due after ten years, weighted average yield (as a percent) |
2.59%
|
2.54%
|
|
| Held-to-maturity Securities, Maturities, Amortized Cost [Abstract] |
|
|
|
| Held-to-maturity Securities, Debt Maturities, after One Through Five Years, Net Carrying Amount |
$ 0
|
|
|
| Held-to-maturity Securities, Debt Maturities, Year Two Through Five, Fair Value |
0
|
|
|
| Due after five years through 10 years, amortized cost |
61
|
$ 58
|
|
| Due after 10 years, amortized cost |
1,150
|
1,210
|
|
| Amortized Cost |
1,211
|
1,268
|
$ 0
|
| Held-to-Maturity Securities, Maturities, Fair Value [Abstract] |
|
|
|
| Due after five years through 10 years, estimated fair value |
64
|
57
|
|
| Due after 10 years, estimated fair value |
1,173
|
1,205
|
|
| Fair Value |
$ 1,237
|
$ 1,262
|
|
| Held-to-maturity Securities, Maturities, Weighted Average Yield [Abstract] |
|
|
|
| Held-to-maturity Securities, Debt Maturities, Year Two Through Five, Weighted Average Yield |
0.00%
|
|
|
| Due after five years through 10 years, weighted-average yield (percent) |
2.50%
|
2.48%
|
|
| Due after 10 years, weighted-average yield (percent) |
2.40%
|
2.41%
|
|