Junior Subordinated Debentures (Junior Subordinated Debentures) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 475,427
Carrying value, at fair value	266,875	$ 262,209
Junior subordinated debentures, at amortized cost	100,690	$ 100,931
Carrying Value	367,565
Junior Subordinated Debt, at Fair Value
Junior Subordinated Debentures [Line Items]
Issued Amount	379,390
Carrying value, at fair value	266,875
Junior Subordinated Debt, at Fair Value | Umpqua Statutory Trust II
Junior Subordinated Debentures [Line Items]
Issued Amount	20,619
Carrying value, at fair value	$ 16,015
Variable rate basis	LIBOR
Basis spread on LIBOR	3.35%
Effective rate	6.00%
Junior Subordinated Debt, at Fair Value | Umpqua Statutory Trust III
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 30,928
Carrying value, at fair value	$ 24,172
Variable rate basis	LIBOR
Basis spread on LIBOR	3.45%
Effective rate	6.10%
Junior Subordinated Debt, at Fair Value | Umpqua Statutory Trust IV
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 10,310
Carrying value, at fair value	$ 7,641
Variable rate basis	LIBOR
Basis spread on LIBOR	2.85%
Effective rate	5.60%
Junior Subordinated Debt, at Fair Value | Umpqua Statutory Trust V
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 10,310
Carrying value, at fair value	$ 7,585
Variable rate basis	LIBOR
Basis spread on LIBOR	2.85%
Effective rate	5.67%
Junior Subordinated Debt, at Fair Value | Umpqua Master Trust I
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 41,238
Carrying value, at fair value	$ 25,650
Variable rate basis	LIBOR
Basis spread on LIBOR	1.35%
Effective rate	4.29%
Junior Subordinated Debt, at Fair Value | Umpqua Master Trust IB
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 20,619
Carrying value, at fair value	$ 14,593
Variable rate basis	LIBOR
Basis spread on LIBOR	2.75%
Effective rate	5.75%
Junior Subordinated Debt, at Fair Value | Sterling Capital Trust III
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 14,433
Carrying value, at fair value	$ 11,664
Variable rate basis	LIBOR
Basis spread on LIBOR	3.25%
Effective rate	5.64%
Junior Subordinated Debt, at Fair Value | Sterling Capital Trust IV
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 10,310
Carrying value, at fair value	$ 8,245
Variable rate basis	LIBOR
Basis spread on LIBOR	3.15%
Effective rate	5.58%
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	$ 16,500
Variable rate basis	LIBOR
Basis spread on LIBOR	3.25%
Effective rate	5.72%
Junior Subordinated Debt, at Fair Value | Sterling Capital Trust VI
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 10,310
Carrying value, at fair value	$ 8,208
Variable rate basis	LIBOR
Basis spread on LIBOR	3.20%
Effective rate	5.68%
Junior Subordinated Debt, at Fair Value | Sterling Capital Trust VII
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 56,702
Carrying value, at fair value	$ 36,457
Variable rate basis	LIBOR
Basis spread on LIBOR	1.53%
Effective rate	4.42%
Junior Subordinated Debt, at Fair Value | Sterling Capital Trust VIII
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 51,547
Carrying value, at fair value	$ 33,384
Variable rate basis	LIBOR
Basis spread on LIBOR	1.63%
Effective rate	4.55%
Junior Subordinated Debt, at Fair Value | Sterling Capital Trust IX
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 46,392
Carrying value, at fair value	$ 29,095
Variable rate basis	LIBOR
Basis spread on LIBOR	1.40%
Effective rate	4.30%
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	$ 7,362
Variable rate basis	LIBOR
Basis spread on LIBOR	3.15%
Effective rate	5.65%
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	$ 6,937
Variable rate basis	LIBOR
Basis spread on LIBOR	1.80%
Effective rate	4.64%
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	$ 13,367
Variable rate basis	LIBOR
Basis spread on LIBOR	3.75%
Effective rate	6.02%
Junior Subordinated Debt, at Amortized Cost
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 96,037
Junior subordinated debentures, at amortized cost	100,690
Junior Subordinated Debt, at Amortized Cost | HB Capital Trust I
Junior Subordinated Debentures [Line Items]
Issued Amount	5,310
Junior subordinated debentures, at amortized cost	$ 6,008
Stated interest rate	10.875%
Effective rate	8.68%
Junior Subordinated Debt, at Amortized Cost | Humboldt Bancorp Statutory Trust I
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 5,155
Junior subordinated debentures, at amortized cost	$ 5,673
Stated interest rate	10.20%
Effective rate	8.58%
Junior Subordinated Debt, at Amortized Cost | Humboldt Bancorp Statutory Trust II
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 10,310
Junior subordinated debentures, at amortized cost	$ 11,070
Variable rate basis	LIBOR
Basis spread on LIBOR	3.60%
Effective rate	4.10%
Junior Subordinated Debt, at Amortized Cost | Humboldt Bancorp Statutory Trust III
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 27,836
Junior subordinated debentures, at amortized cost	$ 29,856
Variable rate basis	LIBOR
Basis spread on LIBOR	2.95%
Effective rate	3.55%
Junior Subordinated Debt, at Amortized Cost | CIB Capital Trust
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 10,310
Junior subordinated debentures, at amortized cost	$ 10,967
Variable rate basis	LIBOR
Basis spread on LIBOR	3.45%
Effective rate	4.08%
Junior Subordinated Debt, at Amortized Cost | Western Sierra Statutory Trust I
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 6,186
Junior subordinated debentures, at amortized cost	$ 6,186
Variable rate basis	LIBOR
Basis spread on LIBOR	3.58%
Effective rate	4.89%
Junior Subordinated Debt, at Amortized Cost | Western Sierra Statutory Trust II
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 10,310
Junior subordinated debentures, at amortized cost	$ 10,310
Variable rate basis	LIBOR
Basis spread on LIBOR	3.60%
Effective rate	4.92%
Junior Subordinated Debt, at Amortized Cost | Western Sierra Statutory Trust III
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 10,310
Junior subordinated debentures, at amortized cost	$ 10,310
Variable rate basis	LIBOR
Basis spread on LIBOR	2.90%
Effective rate	4.20%
Junior Subordinated Debt, at Amortized Cost | Western Sierra Statutory Trust IV
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 10,310
Junior subordinated debentures, at amortized cost	$ 10,310
Variable rate basis	LIBOR
Basis spread on LIBOR	2.90%
Effective rate	4.20%