Business Combinations (Narrative) (Details) (USD $)	12 Months Ended		12 Months Ended											12 Months Ended							0 Months Ended	12 Months Ended	0 Months Ended	12 Months Ended	0 Months Ended	12 Months Ended
	Dec. 31, 2010	Dec. 31, 2011	Dec. 31, 2011 Evergreen Bank [Member]	Dec. 31, 2011 Evergreen Bank [Member] Non-Single Family Residential [Member]	Dec. 31, 2011 Evergreen Bank [Member] Single Family Residential [Member]	Dec. 31, 2011 Evergreen Bank [Member] FDIC Loss and Loss Recovery Sharing And Absorption Threshold Minimum [Member]	Dec. 31, 2011 Evergreen Bank [Member] FDIC Loss and Loss Recovery Sharing And Absorption Threshold Maximum [Member]	Dec. 31, 2011 Rainier Pacific Bank [Member]	Feb. 26, 2010 Rainier Pacific Bank [Member]	Dec. 31, 2011 Rainier Pacific Bank [Member] Non-Single Family Residential [Member]	Dec. 31, 2011 Rainier Pacific Bank [Member] Single Family Residential [Member]	Dec. 31, 2011 Rainier Pacific Bank [Member] FDIC Loss and Loss Recovery Sharing And Absorption Threshold Minimum [Member]	Dec. 31, 2011 Rainier Pacific Bank [Member] FDIC Loss and Loss Recovery Sharing And Absorption Threshold Maximum [Member]	Dec. 31, 2011 Evergreen And Rainier [Member]	Dec. 31, 2010 Evergreen And Rainier [Member]	Dec. 31, 2011 Nevada Security Bank [Member]	Dec. 31, 2010 Nevada Security Bank [Member]	Dec. 31, 2011 Nevada Security Bank [Member] Non-Single Family Residential [Member]	Dec. 31, 2011 Nevada Security Bank [Member] Single Family Residential [Member]	Dec. 31, 2011 Nevada Security Bank [Member] FDIC Loss and Loss Recovery Sharing And Absorption [Member]	Jan. 22, 2010 Evergreen Bank [Member]	Dec. 31, 2011 Evergreen Bank [Member]	Feb. 26, 2010 Rainier Pacific Bank [Member]	Dec. 31, 2011 Rainier Pacific Bank [Member]	Jun. 18, 2010 Nevada Security Bank [Member]	Dec. 31, 2011 Nevada Security Bank [Member]	Dec. 31, 2010 Evergreen And Rainier [Member]
Date that Umpqua Bank assumed operations																						January 22, 2010		February 26, 2010		June 18, 2010
FDIC loss absorption percentage						80.00%	95.00%					80.00%	95.00%							80.00%
FDIC loss recoveries absorption percentage						80.00%	95.00%					80.00%	95.00%							80.00%
Covered asset value for FDIC absorption						$ 90,000,000	$ 90,000,000					$ 95,000,000	$ 95,000,000
Umpqua to incur losses before loss-sharing, amount		30,200,000
Length of loss-sharing arrangement, by loan type, years				5	10					5	10							5	10
Length of loss recovery provisions, by loan type, years				8	10					8	10							8	10
Number of store locations assumed			6					14								5
Business acquisition revenue														46,200,000	54,000,000	18,600,000	15,100,000
Non-interest expense from acquisition, included in Umpqua operations														25,300,000	23,600,000	11,300,000	7,300,000
Earnings (loss) added by acquisition, included in Umpqua operations														13,800,000	11,000,000	2,100,000	1,300,000
Bargain purchase gain on acquisition	6,437,000		6,400,000																		6,437,000						6,400,000
Merger-related expenses, incurred in connection with acquisitions														92,000	4,400,000	101,000	1,700,000
Cost basis net assets (liabilities)			58,800,000					50,300,000								53,600,000
Cash payment received from (paid to) the FDIC								59,400,000								30,000,000
(Goodwill) recognized in connection with acquisition								27,600,000	35,800,000							10,400,000								36,800,000
Core deposit intangible assets recognized and deductible for income tax purposes																								1,100,000		322,000
Purchase of furniture equipment and real estate			344,000					26,300,000																		2,000,000
Total assets acquired																					$ 353,279,000		$ 721,174,000		$ 437,595,000