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Summary of Significant Accounting Principles and Practices - Schedule of Topic 606 Impact on the Income Statement (Details) - USD ($) $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2018 | Sep. 30, 2018 | Jun. 30, 2018 | Mar. 31, 2018 | Dec. 31, 2017 | Sep. 30, 2017 | Jun. 30, 2017 | Mar. 31, 2017 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Revenue |  |  |  |  |  |  |  |  |  |  |
Total revenue | $ 2,770 | $ 2,349 | $ 2,561 | $ 3,090 | $ 2,909 | $ 2,340 | $ 2,368 | $ 2,381 | $ 10,770 | $ 9,998 | $ 9,409
Expenses |  |  |  |  |  |  |  |  |  |  |
Compensation and benefits |  |  |  |  |  |  |  |  | 6,103 | 6,003 | 5,514
Other general expenses |  |  |  |  |  |  |  |  | 1,500 | 1,272 | 1,036
Other income (expense) |  |  |  |  |  |  |  |  | (25) | (125) | (137)
Income taxes |  |  |  |  |  |  |  |  | 146 | $ 250 | $ 148
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09 |  |  |  |  |  |  |  |  |  |  |
Revenue |  |  |  |  |  |  |  |  |  |  |
Total revenue |  |  |  |  |  |  |  |  | (61) |  |
Expenses |  |  |  |  |  |  |  |  |  |  |
Compensation and benefits |  |  |  |  |  |  |  |  | 51 |  |
Other general expenses |  |  |  |  |  |  |  |  | (1) |  |
Other income (expense) |  |  |  |  |  |  |  |  | 1 |  |
Income taxes |  |  |  |  |  |  |  |  | (34) |  |
Calculated under Revenue Guidance in Effect before Topic 606 |  |  |  |  |  |  |  |  |  |  |
Revenue |  |  |  |  |  |  |  |  |  |  |
Total revenue |  |  |  |  |  |  |  |  | 10,709 |  |
Expenses |  |  |  |  |  |  |  |  |  |  |
Compensation and benefits |  |  |  |  |  |  |  |  | 6,154 |  |
Other general expenses |  |  |  |  |  |  |  |  | 1,499 |  |
Other income (expense) |  |  |  |  |  |  |  |  | (24) |  |
Income taxes |  |  |  |  |  |  |  |  | $ 112 |  |

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