Segment Information (Revenues and Asset Management Revenues) (Details) - USD ($) $ in Millions |
3 Months Ended | 12 Months Ended | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
Dec. 31, 2017 |
Sep. 30, 2017 |
Jun. 30, 2017 |
Mar. 31, 2017 |
Dec. 31, 2016 |
Sep. 30, 2016 |
Jun. 30, 2016 |
Mar. 31, 2016 |
Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
|
| Segment Reporting Information [Line Items] | |||||||||||
| Total revenues | $ 16,265 | $ 16,313 | $ 13,441 | $ 13,670 | $ 13,050 | $ 16,961 | $ 14,439 | $ 14,329 | $ 59,689 | $ 58,779 | $ 57,119 |
| Investment Management Division | Investment Management | Intersegment Eliminations | |||||||||||
| Segment Reporting Information [Line Items] | |||||||||||
| Total revenues | 717 | 682 | 682 | ||||||||
| Domestic operations | |||||||||||
| Segment Reporting Information [Line Items] | |||||||||||
| Total revenues | 36,573 | 36,079 | 36,151 | ||||||||
| Foreign operations | |||||||||||
| Segment Reporting Information [Line Items] | |||||||||||
| Total revenues | 23,116 | 22,700 | 20,968 | ||||||||
| Foreign operations, Japan | |||||||||||
| Segment Reporting Information [Line Items] | |||||||||||
| Total revenues | 19,589 | 19,768 | 18,177 | ||||||||
| Foreign operations, Korea | |||||||||||
| Segment Reporting Information [Line Items] | |||||||||||
| Total revenues | $ 1,567 | $ 1,439 | $ 1,462 | ||||||||