Variable Interest Entities Reflects adoption of ASU 2015-12 - Balances Relating to Variable Interest Entities in which BlackRock is Not Primary Beneficiary (Detail) - Variable Interest Entity, Not Primary Beneficiary [Member] - USD ($) |
Jun. 30, 2017 |
Dec. 31, 2016 |
|---|---|---|
| Investments [Member] | ||
| Variable Interest Entity [Line Items] | ||
| Sponsored investment products | $ 228,000,000 | $ 171,000,000 |
| Advisory Fee Receivables [Member] | ||
| Variable Interest Entity [Line Items] | ||
| Sponsored investment products | 12,000,000 | 9,000,000 |
| Other Net Assets (Liabilities) [Member] | ||
| Variable Interest Entity [Line Items] | ||
| Sponsored investment products | (7,000,000) | (8,000,000) |
| Maximum Risk of Loss [Member] | ||
| Variable Interest Entity [Line Items] | ||
| Sponsored investment products | $ 257,000,000 | $ 197,000,000 |