Junior Subordinated Debentures (Junior Subordinated Debentures) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Junior Subordinated Debentures [Line Items]
Issued amount	$ 464,962
Carrying value, at fair value	255,217	$ 274,812
Carrying value, at amortized cost	88,268	$ 88,496
Carrying value	343,485
Junior Subordinated Debt, at Fair Value
Junior Subordinated Debentures [Line Items]
Issued amount	379,390
Carrying value, at fair value	255,217
Junior Subordinated Debt, at Fair Value | Umpqua Statutory Trust II
Junior Subordinated Debentures [Line Items]
Issued amount	20,619
Carrying value, at fair value	$ 16,606
Variable rate basis	LIBOR
Basis spread on LIBOR	3.35%
Effective rate	4.43%
Junior Subordinated Debt, at Fair Value | Umpqua Statutory Trust III
Junior Subordinated Debentures [Line Items]
Issued amount	$ 30,928
Carrying value, at fair value	$ 25,145
Variable rate basis	LIBOR
Basis spread on LIBOR	3.45%
Effective rate	4.52%
Junior Subordinated Debt, at Fair Value | Umpqua Statutory Trust IV
Junior Subordinated Debentures [Line Items]
Issued amount	$ 10,310
Carrying value, at fair value	$ 7,739
Variable rate basis	LIBOR
Basis spread on LIBOR	2.85%
Effective rate	4.11%
Junior Subordinated Debt, at Fair Value | Umpqua Statutory Trust V
Junior Subordinated Debentures [Line Items]
Issued amount	$ 10,310
Carrying value, at fair value	$ 7,653
Variable rate basis	LIBOR
Basis spread on LIBOR	2.85%
Effective rate	4.15%
Junior Subordinated Debt, at Fair Value | Umpqua Master Trust I
Junior Subordinated Debentures [Line Items]
Issued amount	$ 41,238
Carrying value, at fair value	$ 22,875
Variable rate basis	LIBOR
Basis spread on LIBOR	1.35%
Effective rate	2.82%
Junior Subordinated Debt, at Fair Value | Umpqua Master Trust IB
Junior Subordinated Debentures [Line Items]
Issued amount	$ 20,619
Carrying value, at fair value	$ 14,303
Variable rate basis	LIBOR
Basis spread on LIBOR	2.75%
Effective rate	4.28%
Junior Subordinated Debt, at Fair Value | Sterling Capital Trust III
Junior Subordinated Debentures [Line Items]
Issued amount	$ 14,433
Carrying value, at fair value	$ 11,461
Variable rate basis	LIBOR
Basis spread on LIBOR	3.25%
Effective rate	4.36%
Junior Subordinated Debt, at Fair Value | Sterling Capital Trust IV
Junior Subordinated Debentures [Line Items]
Issued amount	$ 10,310
Carrying value, at fair value	$ 8,052
Variable rate basis	LIBOR
Basis spread on LIBOR	3.15%
Effective rate	4.32%
Junior Subordinated Debt, at Fair Value | Sterling Capital Statutory Trust V
Junior Subordinated Debentures [Line Items]
Issued amount	$ 20,619
Carrying value, at fair value	$ 16,201
Variable rate basis	LIBOR
Basis spread on LIBOR	3.25%
Effective rate	4.46%
Junior Subordinated Debt, at Fair Value | Sterling Capital Trust VI
Junior Subordinated Debentures [Line Items]
Issued amount	$ 10,310
Carrying value, at fair value	$ 8,006
Variable rate basis	LIBOR
Basis spread on LIBOR	3.20%
Effective rate	4.40%
Junior Subordinated Debt, at Fair Value | Sterling Capital Trust VII
Junior Subordinated Debentures [Line Items]
Issued amount	$ 56,702
Carrying value, at fair value	$ 33,456
Variable rate basis	LIBOR
Basis spread on LIBOR	1.53%
Effective rate	2.95%
Junior Subordinated Debt, at Fair Value | Sterling Capital Trust VIII
Junior Subordinated Debentures [Line Items]
Issued amount	$ 51,547
Carrying value, at fair value	$ 30,553
Variable rate basis	LIBOR
Basis spread on LIBOR	1.63%
Effective rate	3.12%
Junior Subordinated Debt, at Fair Value | Sterling Capital Trust IX
Junior Subordinated Debentures [Line Items]
Issued amount	$ 46,392
Carrying value, at fair value	$ 26,116
Variable rate basis	LIBOR
Basis spread on LIBOR	1.40%
Effective rate	2.89%
Junior Subordinated Debt, at Fair Value | Lynnwood Financial Statutory Trust I
Junior Subordinated Debentures [Line Items]
Issued amount	$ 9,279
Carrying value, at fair value	$ 7,224
Variable rate basis	LIBOR
Basis spread on LIBOR	3.15%
Effective rate	4.37%
Junior Subordinated Debt, at Fair Value | Lynnwood Financial Statutory Trust II
Junior Subordinated Debentures [Line Items]
Issued amount	$ 10,310
Carrying value, at fair value	$ 6,500
Variable rate basis	LIBOR
Basis spread on LIBOR	1.80%
Effective rate	3.20%
Junior Subordinated Debt, at Fair Value | Klamath First Capital Trust I
Junior Subordinated Debentures [Line Items]
Issued amount	$ 15,464
Carrying value, at fair value	$ 13,327
Variable rate basis	LIBOR
Basis spread on LIBOR	3.75%
Effective rate	4.72%
Junior Subordinated Debt, at Amortized Cost
Junior Subordinated Debentures [Line Items]
Issued amount	$ 85,572
Carrying value, at amortized cost	88,268
Junior Subordinated Debt, at Amortized Cost | Humboldt Bancorp Statutory Trust II
Junior Subordinated Debentures [Line Items]
Issued amount	10,310
Carrying value, at amortized cost	$ 10,895
Variable rate basis	LIBOR
Basis spread on LIBOR	3.60%
Effective rate	3.13%
Junior Subordinated Debt, at Amortized Cost | Humboldt Bancorp Statutory Trust III
Junior Subordinated Debentures [Line Items]
Issued amount	$ 27,836
Carrying value, at amortized cost	$ 29,432
Variable rate basis	LIBOR
Basis spread on LIBOR	2.95%
Effective rate	2.56%
Junior Subordinated Debt, at Amortized Cost | CIB Capital Trust
Junior Subordinated Debentures [Line Items]
Issued amount	$ 10,310
Carrying value, at amortized cost	$ 10,825
Variable rate basis	LIBOR
Basis spread on LIBOR	3.45%
Effective rate	3.09%
Junior Subordinated Debt, at Amortized Cost | Western Sierra Statutory Trust I
Junior Subordinated Debentures [Line Items]
Issued amount	$ 6,186
Carrying value, at amortized cost	$ 6,186
Variable rate basis	LIBOR
Basis spread on LIBOR	3.58%
Effective rate	3.79%
Junior Subordinated Debt, at Amortized Cost | Western Sierra Statutory Trust II
Junior Subordinated Debentures [Line Items]
Issued amount	$ 10,310
Carrying value, at amortized cost	$ 10,310
Variable rate basis	LIBOR
Basis spread on LIBOR	3.60%
Effective rate	3.84%
Junior Subordinated Debt, at Amortized Cost | Western Sierra Statutory Trust III
Junior Subordinated Debentures [Line Items]
Issued amount	$ 10,310
Carrying value, at amortized cost	$ 10,310
Variable rate basis	LIBOR
Basis spread on LIBOR	2.90%
Effective rate	3.14%
Junior Subordinated Debt, at Amortized Cost | Western Sierra Statutory Trust IV
Junior Subordinated Debentures [Line Items]
Issued amount	$ 10,310
Carrying value, at amortized cost	$ 10,310
Variable rate basis	LIBOR
Basis spread on LIBOR	2.90%
Effective rate	3.14%