v3.8.0.1
Significant Accounting Policies - Impact of ASU 2014-09 Adoption to Condensed Consolidated Statement of Income (Detail) - USD ($)
$ / shares in Units, $ in Millions
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Significant Accounting Policies [Line Items]    
Total revenue $ 3,583 $ 3,092
Total expense 2,208 1,949
Operating income 1,375 1,143
Income tax expense 265 268
Net income 1,094 868
Net income attributable to BlackRock, Inc. $ 1,089 $ 859
Earnings per share attributable to BlackRock, Inc. common stockholders:    
Basic $ 6.75 $ 5.27
Diluted $ 6.68 $ 5.21
Accounting Standards Update 2014-09 [Member] | Previously Reported [Member]    
Significant Accounting Policies [Line Items]    
Total revenue   $ 2,824
Total expense   1,677
Operating income   1,147
Income tax expense   269
Net income   871
Net income attributable to BlackRock, Inc.   $ 862
Earnings per share attributable to BlackRock, Inc. common stockholders:    
Basic   $ 5.29
Diluted   $ 5.23
Accounting Standards Update 2014-09 [Member] | Adoption of the New Revenue Standard Adjustment [Member]    
Significant Accounting Policies [Line Items]    
Total revenue   $ 268
Total expense   272
Operating income   (4)
Income tax expense   (1)
Net income   (3)
Net income attributable to BlackRock, Inc.   $ (3)
Earnings per share attributable to BlackRock, Inc. common stockholders:    
Basic   $ (0.02)
Diluted   $ (0.02)