Washington Banking Company Information - Condensed Statements of Income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Condensed Financial Statements, Captions [Line Items]
Interest on taxable investment securities									$ 5,720	$ 5,333	$ 3,967
Total interest income	18,554	18,469	18,726	19,610	21,439	22,262	22,726	23,283	75,359	89,710	89,707
Interest on junior subordinated debentures									478	532	489
Total interest expense	1,301	1,322	1,369	1,428	1,585	1,710	1,837	1,981	5,420	7,113	9,981
Noninterest expense	16,436	13,072	12,926	13,867	13,972	13,663	15,109	13,655	56,301	56,399	55,825
Loss before income tax benefit and undistributed earnings of subsidiaries	3,606	6,687	4,364	6,711	6,739	6,997	4,020	6,944	21,368	24,700	23,063
Income tax benefit	1,104	2,185	1,456	2,127	2,153	2,359	1,173	2,171	6,872	7,856	7,111
Net income before preferred dividends									14,496	16,844	15,952
Preferred dividends											(38)
Net income available to common shareholders	2,502	4,502	2,908	4,584	4,586	4,638	2,847	4,773	14,496	16,844	14,868
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Interest on taxable investment securities									14	16	15
Total interest income									14	16	15
Interest on junior subordinated debentures									478	532	489
Total interest expense									478	532	489
Noninterest expense									1,432	1,057	905
Loss before income tax benefit and undistributed earnings of subsidiaries									(1,896)	(1,573)	(1,379)
Income tax benefit									(664)	(550)	(482)
Loss before undistributed earnings of subsidiaries									(1,232)	(1,023)	(897)
Undistributed earnings of subsidiaries									6,878	8,967	11,949
Investment Income, Dividend									8,850	8,900	4,900
Net income before preferred dividends									14,496	16,844	15,952
Preferred dividends									0	0	1,084
Net income available to common shareholders									$ 14,496	$ 16,844	$ 14,868