With only $39 billion under management (that is, other people's money), the Carlyle group(凯雷投资集团)claims to be “one of the world’s largest”.
The revenue for 2005 alone in a mainstream Investment Bank (Goldman) is close to 25 billion.(https://www.gs.com/our_firm/investor_relations/financial_reports/annual_reports/2005/)
Talking about a small fish like the Carlyle group is not helpful in getting an accurate picture of investment banks in the US.