Trust Preferred Securities and Junior Subordinated Debentures (Details) (USD $) In Millions, unless otherwise specified	0 Months Ended		3 Months Ended	12 Months Ended
	Jun. 29, 2007 Washington Banking Capital Trust I [Member]	Jun. 27, 2002 Washington Banking Capital Trust I [Member]	Jun. 30, 2007 Washington Banking Master Trust [Member]	Dec. 31, 2012 Washington Banking Master Trust [Member]
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Trust preferred securities issued		$ 15	$ 25
Maturity period of trust preferred securities		30 years	30 years
Minimum callable period for trust preferred securities		5 years	5 years
Redemption amount of trust preferred securities issued	$ 15
Trust preferred securities, description of variable rate basis				London Interbank Offered Rate ("LIBOR") plus
Trust preferred securities, basis spread on variable rate (in hundredths)				1.56%
Trust preferred securities, interest rate (in hundredths)				1.95%