Other Assets - Additional Information (Detail) - USD ($) shares in Millions, $ in Millions |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2015 |
Dec. 31, 2014 |
Dec. 31, 2013 |
|
| Other Assets [Line Items] | |||
| Gain related to PennyMac initial public offering | $ 0 | $ 0 | $ 39 |
| Charitable contribution | 0 | 0 | 124 |
| Gain related to the Charitable Contribution | $ 0 | 0 | 80 |
| PennyMac [Member] | |||
| Other Assets [Line Items] | |||
| Gain related to PennyMac initial public offering | $ 39 | ||
| Charitable Contribution, by units | 6.1 | ||
| Charitable contribution | $ 124 | ||
| Gain related to the Charitable Contribution | 80 | ||
| Tax benefit related to Charitable Contribution | $ 48 | ||
| Ownership percentage | 20.00% | ||
| Shares and units | 16.0 | ||
| Carrying value - equity method investment | $ 222 | 167 | |
| Fair value of equity method investments | $ 239 | $ 269 | |