Regulatory Capital (Summary of Company's Capital Amounts And Ratios) (Details) $ in Thousands	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Consolidated
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Capital	$ 3,347,926	$ 3,104,444
Capital to Risk Weighted Assets	0.1563	0.1396
Capital Required for Capital Adequacy	$ 1,713,891	$ 1,779,265
Capital Required for Capital Adequacy to Risk Weighted Assets	0.0800	0.0800
Capital Required to be Well Capitalized	$ 2,142,364	$ 2,224,081
Capital Required to be Well Capitalized to Risk Weighted Assets	0.1000	0.1000
Tier One Risk Based Capital	$ 2,636,194	$ 2,490,709
Tier One Risk Based Capital to Risk Weighted Assets	0.1231	0.1120
Tier One Risk Based Capital Required for Capital Adequacy	$ 1,285,418	$ 1,334,449
Tier One Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets	0.0600	0.0600
Tier One Risk Based Capital Required to be Well Capitalized	$ 1,713,891	$ 1,779,265
Tier One Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets	0.0800	0.0800
Common Equity Tier One Capital	$ 2,636,194	$ 2,490,709
Common Equity Tier One Capital Ratio	0.1231	0.1120
Common Equity Tier One Capital Required for Capital Adequacy	$ 964,064	$ 1,000,837
Tier One Common Equity Required for Capital Adequacy to Risk Weighted Assets	4.50%	4.50%
Common Equity Tier One Capital Required to be Well-Capitalized	$ 1,392,536	$ 1,445,653
Tier One Common Equity Required to be Well Capitalized to Risk Weighted Assets	6.50%	6.50%
Tier One Leverage Capital	$ 2,636,194	$ 2,490,709
Tier One Leverage Capital to Average Assets	0.0898	0.0916
Tier One Leverage Capital Required for Capital Adequacy	$ 1,174,129	$ 1,087,509
Tier One Leverage Capital Required for Capital Adequacy to Average Assets	0.0400	0.0400
Tier One Leverage Capital Required to be Well Capitalized	$ 1,467,661	$ 1,359,387
Tier One Leverage Capital Required to be Well Capitalized to Average Assets	0.0500	0.0500
Umpqua Bank
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Capital	$ 3,134,116	$ 2,945,830
Capital to Risk Weighted Assets	0.1463	0.1326
Capital Required for Capital Adequacy	$ 1,713,809	$ 1,777,265
Capital Required for Capital Adequacy to Risk Weighted Assets	0.0800	0.0800
Capital Required to be Well Capitalized	$ 2,142,262	$ 2,221,581
Capital Required to be Well Capitalized to Risk Weighted Assets	0.1000	0.1000
Tier One Risk Based Capital	$ 2,873,383	$ 2,783,095
Tier One Risk Based Capital to Risk Weighted Assets	0.1341	0.1253
Tier One Risk Based Capital Required for Capital Adequacy	$ 1,285,357	$ 1,332,949
Tier One Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets	0.0600	0.0600
Tier One Risk Based Capital Required to be Well Capitalized	$ 1,713,809	$ 1,777,265
Tier One Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets	0.0800	0.0800
Common Equity Tier One Capital	$ 2,873,383	$ 2,783,095
Common Equity Tier One Capital Ratio	0.1341	0.1253
Common Equity Tier One Capital Required for Capital Adequacy	$ 964,018	$ 999,712
Tier One Common Equity Required for Capital Adequacy to Risk Weighted Assets	4.50%	4.50%
Common Equity Tier One Capital Required to be Well-Capitalized	$ 1,392,470	$ 1,444,028
Tier One Common Equity Required to be Well Capitalized to Risk Weighted Assets	6.50%	6.50%
Tier One Leverage Capital	$ 2,873,383	$ 2,783,095
Tier One Leverage Capital to Average Assets	0.0979	0.1024
Tier One Leverage Capital Required for Capital Adequacy	$ 1,174,065	$ 1,086,999
Tier One Leverage Capital Required for Capital Adequacy to Average Assets	0.0400	0.0400
Tier One Leverage Capital Required to be Well Capitalized	$ 1,467,581	$ 1,358,749
Tier One Leverage Capital Required to be Well Capitalized to Average Assets	0.0500	0.0500