Note 6 - Other Assets (Details)	9 Months Ended
Sep. 30, 2014
Disclosure Text Block Supplement [Abstract]
FRB Membership, Stock Subscription, Percent of Paid-Up Capital Stock and Surplus Requirement	6.00%
FHLB Borrowings, Minimum Activity-Based Requirement Percentage of Oustanding Advances	4.70%

For a bank applying for membership in the Federal Reserve System, this represents the percentage of the bank's paid-up capital stock and surplus which is required to be subscribed to stock in the Federal Reserve Bank.

No definition available.

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Namespace Prefix:	wabc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration