Washington Banking Company Information - Condensed Statements of Cash Flows (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Condensed Financial Statements, Captions [Line Items]
Net income before preferred dividends	$ 14,496	$ 16,844	$ 15,952
Net decrease (increase) in other assets	20,763	18,745	18,349
Net (decrease) increase in other liabilities	(5,514)	8,562	2,897
Cash flows provided by operating activities	63,633	70,906	51,777
Cash flows provided by investing activities	(36,197)	(58,490)	29,134
Redemption of preferred stock	0	0	(26,380)
Repurchase of common stock warrant	0	0	(1,625)
Dividends paid on preferred stock	0	0	(38)
Dividends paid on common stock	(8,299)	(7,717)	(3,068)
Proceeds from issuance of common stock under stock plans	124	301	301
Net cash used in financing activities	(3,651)	(10,756)	(56,685)
Net change in cash and cash equivalents	23,785	1,660	24,226
Cash and cash equivalents at beginning of period	107,573	105,913	81,687
Cash and cash equivalents at end of period	131,358	107,573	105,913
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Net income before preferred dividends	14,496	16,844	15,952
Equity in undistributed earnings of subsidiaries	(6,878)	(8,967)	(11,949)
Net decrease (increase) in other assets	467	(524)	(490)
Net (decrease) increase in other liabilities	86	(3)	(168)
Cash flows provided by operating activities	8,171	7,350	3,345
Investment in subsidiaries	0	0	31,382
Cash flows provided by investing activities	0	0	31,382
Redemption of preferred stock	0	0	(26,380)
Repurchase of common stock warrant	0	0	(1,625)
Dividends paid on preferred stock	0	0	(38)
Dividends paid on common stock	(8,299)	(7,717)	(3,068)
Proceeds from issuance of common stock under stock plans	124	301	301
Net cash used in financing activities	(8,175)	(7,416)	(30,810)
Net change in cash and cash equivalents	(4)	(66)	3,917
Cash and cash equivalents at beginning of period	5,327	5,393	1,476
Cash and cash equivalents at end of period	$ 5,323	$ 5,327	$ 5,393