Investment Securities - Investment Securities Available-for-Sale (Parenthetical) (Detail)	Sep. 30, 2015 CreditScore
Investments, Debt and Equity Securities [Abstract]
Minimum weighted average credit score of prime securities	725
Maximum loan-to-value of prime securities	80.00%

Minimum weighted average credit score of prime securities.

No definition available.

Name:	usb_MinimumCreditScoreOfPrimeSecurities
Namespace Prefix:	usb_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant