Summary of Significant Accounting Policies - Additional Information (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012 Branch_office	Dec. 31, 2011	Dec. 31, 2010
Significant Accounting Policies [Line Items]
Number of offices in Western Oregon and Western Washington	14
Number of offices loan production offices in Tacoma, Washington and Denver, Colorado	2
Junior subordinated debentures	$ 8,248	$ 8,248
Investment in the Trust	248
Reserves with Federal Reserve Bank	1,061	350
Past due loans, nonaccrual period	90 days
Commercial overdrafts charge-off period	90 days
Reserve for unfunded loan commitments	170	205
FHLB minimum required investment	10,462	10,652
Advertising expenses	$ 779	$ 720	$ 569
Common stock were excluded from diluted earnings per share, anti-dilutive effect	452,480	266,859	352,535
Minimum [Member] | Buildings [Member]
Significant Accounting Policies [Line Items]
Estimated useful life	30 years
Minimum [Member] | Furniture and equipment [Member]
Significant Accounting Policies [Line Items]
Estimated useful life	3 years
Maximum [Member] | Buildings [Member]
Significant Accounting Policies [Line Items]
Estimated useful life	40 years
Maximum [Member] | Furniture and equipment [Member]
Significant Accounting Policies [Line Items]
Estimated useful life	10 years