Selected Quarterly Financial Data - Schedule of Selected Quarterly Financial Data (Parenthetical) (Detail) - USD ($) $ in Millions |
3 Months Ended | ||||
|---|---|---|---|---|---|
Dec. 31, 2015 |
Mar. 31, 2015 |
Dec. 31, 2014 |
Sep. 30, 2014 |
Jun. 30, 2014 |
|
| Condensed Financial Statements, Captions [Line Items] | |||||
| Tax benefit related to certain nonrecurring items | $ 69 | $ 39 | $ 34 | ||
| Deferred tax expense (benefit) associated with the revaluation of deferred income tax liabilities as a result of tax changes | $ (64) | $ (32) | $ 23 | ||
| Barclays Global Investors [Member] | |||||
| Condensed Financial Statements, Captions [Line Items] | |||||
| Tax benefit related to resolution of certain outstanding tax matters | 94 | ||||
| Indemnification asset for unrecognized tax benefits | 50 | ||||
| Offsetting tax benefit | 50 | ||||
| General and Administrative Expenses [Member] | Barclays Global Investors [Member] | |||||
| Condensed Financial Statements, Captions [Line Items] | |||||
| Reduction of indemnification asset | $ 50 | ||||