Deposit Accounts (Details) - USD ($) $ in Millions |
Jun. 30, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
|---|---|---|---|
| Deposits [Line Items] | |||
| Total deposits | $ 8,571 | $ 7,935 | $ 7,069 |
| Branch retail deposits | |||
| Deposits [Line Items] | |||
| Demand deposit accounts | 797 | 726 | |
| Savings accounts | 3,717 | 3,428 | |
| Money market demand accounts | 163 | 209 | |
| Certificates of deposit/CDARS | 811 | 807 | |
| Total deposits | 5,488 | 5,170 | |
| Commercial deposits | |||
| Deposits [Line Items] | |||
| Demand deposit accounts | 194 | 133 | |
| Savings accounts | 34 | 27 | |
| Money market demand accounts | 104 | 43 | |
| Certificates of deposit/CDARS | 14 | 5 | |
| Total deposits | 346 | 208 | |
| Retail deposits | |||
| Deposits [Line Items] | |||
| Total deposits | 5,834 | 5,378 | |
| Government deposits | |||
| Deposits [Line Items] | |||
| Demand deposit accounts | 302 | 246 | |
| Savings accounts | 363 | 317 | |
| Certificates of deposit/CDARS | 397 | 355 | |
| Total deposits | 1,062 | 918 | |
| Company controlled deposits | |||
| Deposits [Line Items] | |||
| Total deposits | $ 1,039 | $ 773 |