Subsequent Event (Details) - USD ($) $ in Thousands	Oct. 12, 2021	Sep. 30, 2021	Dec. 31, 2020
Subsequent Event [Line Items]
Total assets		$ 30,891,479	$ 29,235,175
Loans and leases, net		21,712,380	21,450,966
Available for sale, at fair value		3,723,171	2,932,558
Total deposits		26,908,397	24,622,201
Stockholders' Equity Attributable to Parent		2,722,379	$ 2,704,577
Columbia Banking System, Inc. | Umpqua Bank and Columbia Banking System Merger
Subsequent Event [Line Items]
Total assets		18,600,000
Loans and leases, net		9,400,000
Available for sale, at fair value		4,800,000
Total deposits		16,000,000
Stockholders' Equity Attributable to Parent		$ 2,300,000
Subsequent Event
Subsequent Event [Line Items]
Business Acquisition, Equity Interest Issued or Issuable, Share Exchange Ratio	0.5958
Termination Fee	$ 145,000
Subsequent Event | Umpqua Bank and Columbia Banking System Merger
Subsequent Event [Line Items]
Business Acquisition, Percentage of Voting Interests Acquired	62.00%
Subsequent Event | Columbia Banking System, Inc. | Umpqua Bank and Columbia Banking System Merger
Subsequent Event [Line Items]
Business Acquisition, Percentage of Voting Interests Acquired	38.00%