Junior Subordinated Debentures (Junior Subordinated Debentures) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 475,427
AT FAIR VALUE	253,665	$ 249,294
AT AMORTIZED COST	101,334	$ 101,576
Carrying Value	354,999
Junior Subordinated Debt, at Fair Value [Member]
Junior Subordinated Debentures [Line Items]
Issued Amount	379,390
AT FAIR VALUE	253,665
Junior Subordinated Debt, at Fair Value [Member] | Umpqua Statutory Trust II [Member]
Junior Subordinated Debentures [Line Items]
Issued Amount	20,619
AT FAIR VALUE	$ 15,346
Variable Rate Basis	LIBOR
Basis spread on LIBOR	3.35%
Effective Rate	4.89%
Junior Subordinated Debt, at Fair Value [Member] | Umpqua Statutory Trust III [Member]
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 30,928
AT FAIR VALUE	$ 23,202
Variable Rate Basis	LIBOR
Basis spread on LIBOR	3.45%
Effective Rate	5.03%
Junior Subordinated Debt, at Fair Value [Member] | Umpqua Statutory Trust IV [Member]
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 10,310
AT FAIR VALUE	$ 7,276
Variable Rate Basis	LIBOR
Basis spread on LIBOR	2.85%
Effective Rate	4.45%
Junior Subordinated Debt, at Fair Value [Member] | Umpqua Statutory Trust V [Member]
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 10,310
AT FAIR VALUE	$ 7,248
Variable Rate Basis	LIBOR
Basis spread on LIBOR	2.85%
Effective Rate	4.46%
Junior Subordinated Debt, at Fair Value [Member] | Umpqua Master Trust I [Member]
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 41,238
AT FAIR VALUE	$ 24,065
Variable Rate Basis	LIBOR
Basis spread on LIBOR	1.35%
Effective Rate	2.89%
Junior Subordinated Debt, at Fair Value [Member] | Umpqua Master Trust IB [Member]
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 20,619
AT FAIR VALUE	$ 13,985
Variable Rate Basis	LIBOR
Basis spread on LIBOR	2.75%
Effective Rate	4.55%
Junior Subordinated Debt, at Fair Value [Member] | Sterling Capital Trust III [Member]
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 14,433
AT FAIR VALUE	$ 11,263
Variable Rate Basis	LIBOR
Basis spread on LIBOR	3.25%
Effective Rate	4.55%
Junior Subordinated Debt, at Fair Value [Member] | Sterling Capital Trust IV [Member]
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 10,310
AT FAIR VALUE	$ 7,960
Variable Rate Basis	LIBOR
Basis spread on LIBOR	3.15%
Effective Rate	4.50%
Junior Subordinated Debt, at Fair Value [Member] | Sterling Capital Statutory Trust V [Member]
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 20,619
AT FAIR VALUE	$ 15,971
Variable Rate Basis	LIBOR
Basis spread on LIBOR	3.25%
Effective Rate	4.62%
Junior Subordinated Debt, at Fair Value [Member] | Sterling Capital Trust VI [Member]
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 10,310
AT FAIR VALUE	$ 7,934
Variable Rate Basis	LIBOR
Basis spread on LIBOR	3.20%
Effective Rate	4.60%
Junior Subordinated Debt, at Fair Value [Member] | Sterling Capital Trust VII [Member]
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 56,702
AT FAIR VALUE	$ 34,259
Variable Rate Basis	LIBOR
Basis spread on LIBOR	1.53%
Effective Rate	2.52%
Junior Subordinated Debt, at Fair Value [Member] | Sterling Capital Trust VIII [Member]
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 51,547
AT FAIR VALUE	$ 31,462
Variable Rate Basis	LIBOR
Basis spread on LIBOR	1.63%
Effective Rate	3.22%
Junior Subordinated Debt, at Fair Value [Member] | Sterling Capital Trust IX [Member]
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 46,392
AT FAIR VALUE	$ 27,020
Variable Rate Basis	LIBOR
Basis spread on LIBOR	1.40%
Effective Rate	2.81%
Junior Subordinated Debt, at Fair Value [Member] | Lynnwood Financial Statutory Trust I [Member]
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 9,279
AT FAIR VALUE	$ 7,111
Variable Rate Basis	LIBOR
Basis spread on LIBOR	3.15%
Effective Rate	4.54%
Junior Subordinated Debt, at Fair Value [Member] | Lynnwood Financial Statutory Trust II [Member]
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 10,310
AT FAIR VALUE	$ 6,550
Variable Rate Basis	LIBOR
Basis spread on LIBOR	1.80%
Effective Rate	3.36%
Junior Subordinated Debt, at Fair Value [Member] | Klamath First Capital Trust I [Member]
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 15,464
AT FAIR VALUE	$ 13,013
Variable Rate Basis	LIBOR
Basis spread on LIBOR	3.75%
Effective Rate	5.03%
Junior Subordinated Debt, at Amortized Cost [Member]
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 96,037
AT AMORTIZED COST	101,334
Junior Subordinated Debt, at Amortized Cost [Member] | HB Capital Trust I [Member]
Junior Subordinated Debentures [Line Items]
Issued Amount	5,310
AT AMORTIZED COST	$ 6,119
Stated Interest Rate	10.875%
Effective Rate	8.52%
Junior Subordinated Debt, at Amortized Cost [Member] | Humboldt Bancorp Statutory Trust I [Member]
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 5,155
AT AMORTIZED COST	$ 5,751
Stated Interest Rate	10.20%
Effective Rate	8.46%
Junior Subordinated Debt, at Amortized Cost [Member] | Humboldt Bancorp Statutory Trust II [Member]
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 10,310
AT AMORTIZED COST	$ 11,177
Variable Rate Basis	LIBOR
Basis spread on LIBOR	3.60%
Effective Rate	3.15%
Junior Subordinated Debt, at Amortized Cost [Member] | Humboldt Bancorp Statutory Trust III [Member]
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 27,836
AT AMORTIZED COST	$ 30,116
Variable Rate Basis	LIBOR
Basis spread on LIBOR	2.95%
Effective Rate	2.60%
Junior Subordinated Debt, at Amortized Cost [Member] | CIB Capital Trust [Member]
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 10,310
AT AMORTIZED COST	$ 11,055
Variable Rate Basis	LIBOR
Basis spread on LIBOR	3.45%
Effective Rate	3.12%
Junior Subordinated Debt, at Amortized Cost [Member] | Western Sierra Statutory Trust I [Member]
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 6,186
AT AMORTIZED COST	$ 6,186
Variable Rate Basis	LIBOR
Basis spread on LIBOR	3.58%
Effective Rate	3.88%
Junior Subordinated Debt, at Amortized Cost [Member] | Western Sierra Statutory Trust II [Member]
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 10,310
AT AMORTIZED COST	$ 10,310
Variable Rate Basis	LIBOR
Basis spread on LIBOR	3.60%
Effective Rate	3.94%
Junior Subordinated Debt, at Amortized Cost [Member] | Western Sierra Statutory Trust III [Member]
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 10,310
AT AMORTIZED COST	$ 10,310
Variable Rate Basis	LIBOR
Basis spread on LIBOR	2.90%
Effective Rate	3.19%
Junior Subordinated Debt, at Amortized Cost [Member] | Western Sierra Statutory Trust IV [Member]
Junior Subordinated Debentures [Line Items]
Issued Amount	$ 10,310
AT AMORTIZED COST	$ 10,310
Variable Rate Basis	LIBOR
Basis spread on LIBOR	2.90%
Effective Rate	3.19%