Junior Subordinated Debentures (Junior Subordinated Debentures) (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 475,427
Carrying value, at fair value	265,423	$ 262,209
Carrying value, at amortized cost	100,770	$ 100,931
Carrying Value	366,193
Junior Subordinated Debt, at Fair Value
Junior Subordinated Debentures [Line Items]
Issued Amount	379,390
Carrying value, at fair value	265,423
Junior Subordinated Debt, at Fair Value | Umpqua Statutory Trust II
Junior Subordinated Debentures [Line Items]
Issued Amount	20,619
Carrying value, at fair value	$ 15,928
Variable rate basis	LIBOR
Basis spread on LIBOR	3.35%
Effective rate	5.85%
Junior Subordinated Debt, at Fair Value | Umpqua Statutory Trust III
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 30,928
Carrying value, at fair value	$ 24,050
Variable rate basis	LIBOR
Basis spread on LIBOR	3.45%
Effective rate	5.96%
Junior Subordinated Debt, at Fair Value | Umpqua Statutory Trust IV
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 10,310
Carrying value, at fair value	$ 7,594
Variable rate basis	LIBOR
Basis spread on LIBOR	2.85%
Effective rate	5.44%
Junior Subordinated Debt, at Fair Value | Umpqua Statutory Trust V
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 10,310
Carrying value, at fair value	$ 7,541
Variable rate basis	LIBOR
Basis spread on LIBOR	2.85%
Effective rate	5.63%
Junior Subordinated Debt, at Fair Value | Umpqua Master Trust I
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 41,238
Carrying value, at fair value	$ 25,451
Variable rate basis	LIBOR
Basis spread on LIBOR	1.35%
Effective rate	4.21%
Junior Subordinated Debt, at Fair Value | Umpqua Master Trust IB
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 20,619
Carrying value, at fair value	$ 14,517
Variable rate basis	LIBOR
Basis spread on LIBOR	2.75%
Effective rate	5.68%
Junior Subordinated Debt, at Fair Value | Sterling Capital Trust III
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 14,433
Carrying value, at fair value	$ 11,611
Variable rate basis	LIBOR
Basis spread on LIBOR	3.25%
Effective rate	5.49%
Junior Subordinated Debt, at Fair Value | Sterling Capital Trust IV
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 10,310
Carrying value, at fair value	$ 8,209
Variable rate basis	LIBOR
Basis spread on LIBOR	3.15%
Effective rate	5.44%
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	$ 16,434
Variable rate basis	LIBOR
Basis spread on LIBOR	3.25%
Effective rate	5.70%
Junior Subordinated Debt, at Fair Value | Sterling Capital Trust VI
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 10,310
Carrying value, at fair value	$ 8,174
Variable rate basis	LIBOR
Basis spread on LIBOR	3.20%
Effective rate	5.61%
Junior Subordinated Debt, at Fair Value | Sterling Capital Trust VII
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 56,702
Carrying value, at fair value	$ 36,182
Variable rate basis	LIBOR
Basis spread on LIBOR	1.53%
Effective rate	4.34%
Junior Subordinated Debt, at Fair Value | Sterling Capital Trust VIII
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 51,547
Carrying value, at fair value	$ 33,143
Variable rate basis	LIBOR
Basis spread on LIBOR	1.63%
Effective rate	4.47%
Junior Subordinated Debt, at Fair Value | Sterling Capital Trust IX
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 46,392
Carrying value, at fair value	$ 28,852
Variable rate basis	LIBOR
Basis spread on LIBOR	1.40%
Effective rate	4.10%
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	$ 7,330
Variable rate basis	LIBOR
Basis spread on LIBOR	3.15%
Effective rate	5.63%
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	$ 6,888
Variable rate basis	LIBOR
Basis spread on LIBOR	1.80%
Effective rate	4.56%
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	$ 13,519
Variable rate basis	LIBOR
Basis spread on LIBOR	3.75%
Effective rate	5.84%
Junior Subordinated Debt, at Amortized Cost
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 96,037
Carrying value, at amortized cost	100,770
Junior Subordinated Debt, at Amortized Cost | HB Capital Trust I
Junior Subordinated Debentures [Line Items]
Issued Amount	5,310
Carrying value, at amortized cost	$ 6,022
Stated interest rate	10.875%
Effective rate	8.66%
Junior Subordinated Debt, at Amortized Cost | Humboldt Bancorp Statutory Trust I
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 5,155
Carrying value, at amortized cost	$ 5,683
Stated interest rate	10.20%
Effective rate	8.57%
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	$ 11,083
Variable rate basis	LIBOR
Basis spread on LIBOR	3.60%
Effective rate	4.04%
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	$ 29,888
Variable rate basis	LIBOR
Basis spread on LIBOR	2.95%
Effective rate	3.49%
Junior Subordinated Debt, at Amortized Cost | CIB Capital Trust
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 10,310
Carrying value, at amortized cost	$ 10,978
Variable rate basis	LIBOR
Basis spread on LIBOR	3.45%
Effective rate	3.95%
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	4.75%
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	4.87%
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	4.06%
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	4.06%