Subordinated Debentures (Details)						1 Months Ended			3 Months Ended	9 Months Ended
	Oct. 07, 2019 USD ($)	Sep. 16, 2019	Jul. 08, 2019	Jul. 01, 2018 USD ($)	Nov. 01, 2017 USD ($) note	Sep. 30, 2019 USD ($)	May 31, 2019 USD ($)	Mar. 31, 2004 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)	Apr. 01, 2017 USD ($)	Aug. 31, 2014 USD ($)
Subordinated Debentures
Subordinated debentures						$ 217,825,000			$ 217,825,000	$ 217,825,000		$ 110,313,000
Aggregate amount called on subordinated debentures										15,465,000	$ 0
Reduction of Tier 1 capital associated with redemption of capital instruments									14,700,000
PPBI Trust I
Subordinated Debentures
Floating rate trust preferred securities issue amount								$ 10,000,000.0
Notes
Subordinated Debentures
Debt issued														$ 60,000,000.0
Fixed interest rate (as a percent)														5.75%
Subordinated debentures						59,400,000			59,400,000	59,400,000
Unamortized debt issuance cost						598,000			598,000	598,000
Subordinated Debentures | Mission Community Capital Trust I
Subordinated Debentures
Subordinated debentures						$ 2,800,000			$ 2,800,000	$ 2,800,000
Floating rate junior subordinated debt													$ 3,100,000
Effective rate (as a percent)						5.25%			5.25%	5.25%
Purchase accounting fair value adjustments										$ 290,000
Subordinated Debentures | Mission Community Capital Trust I | Subsequent Event
Subordinated Debentures
Floating rate junior subordinated debt	$ 3,100,000
Effective rate (as a percent)	5.25%
Aggregate amount called on subordinated debentures	$ 3,100,000
Loss on early debt extinguishment	$ 290,000
Subordinated Debentures | Santa Lucia Bancorp (CA) Capital Trust
Subordinated Debentures
Subordinated debentures						$ 3,900,000			$ 3,900,000	$ 3,900,000
Floating rate junior subordinated debt													5,200,000
Effective rate (as a percent)						3.78%			3.78%	3.78%
Purchase accounting fair value adjustments										$ 1,300,000
Subordinated Debentures | Heritage Oaks Bancorp
Subordinated Debentures
Floating rate junior subordinated debt						$ 4,000,000.0			$ 4,000,000.0	$ 4,000,000.0			$ 5,200,000
Effective rate (as a percent)						4.04%			4.04%	4.04%
Purchase accounting fair value adjustments										$ 1,200,000
Subordinated Debentures | Plaza Bancorp
Subordinated Debentures
Floating rate junior subordinated debt						$ 25,100,000			$ 25,100,000	25,100,000
Purchase accounting fair value adjustments										139,000
Subordinated Debentures | Grandpoint Capital, Inc.
Subordinated Debentures
Effective rate (as a percent)		5.36%
Aggregate amount called on subordinated debentures				$ 5,200,000
Loss on early debt extinguishment						214,000
Debt assumed in acquisition				$ 5,200,000
Subordinated Debentures | PPBI Trust I
Subordinated Debentures
Debt issued								$ 10,300,000
Minority interest purchased (as a percent)								3.00%
Amount of minority interest purchased								$ 310,000
Effective rate (as a percent)			5.35%
Aggregate amount called on subordinated debentures										$ 10,400,000
Subordinated Debentures | LIBOR | Mission Community Capital Trust I
Subordinated Debentures
Floating interest rate, basis points added to base rate (as a percent)										2.95%
Subordinated Debentures | LIBOR | Mission Community Capital Trust I | Subsequent Event
Subordinated Debentures
Floating interest rate, basis points added to base rate (as a percent)	2.95%
Subordinated Debentures | LIBOR | Santa Lucia Bancorp (CA) Capital Trust
Subordinated Debentures
Floating interest rate, basis points added to base rate (as a percent)										1.48%
Subordinated Debentures | LIBOR | Heritage Oaks Bancorp
Subordinated Debentures
Floating interest rate, basis points added to base rate (as a percent)										1.72%
Subordinated Debentures | LIBOR | Grandpoint Capital, Inc.
Subordinated Debentures
Floating interest rate, basis points added to base rate (as a percent)		2.95%
Subordinated Debentures | LIBOR | PPBI Trust I
Subordinated Debentures
Floating interest rate, basis points added to base rate (as a percent)			2.75%
Subordinated Debentures | Notes II
Subordinated Debentures
Debt issued							$ 125,000,000.0
Fixed interest rate (as a percent)							4.875%
Unamortized debt issuance cost						2,400,000			2,400,000	$ 2,400,000
Public offering price (as a percent)							100.00%
Floating rate junior subordinated debt						$ 122,600,000			$ 122,600,000	$ 122,600,000
Subordinated Debentures | Notes II | LIBOR
Subordinated Debentures
Floating interest rate, basis points added to base rate (as a percent)							2.50%
Subordinated Notes 7.125% | Plaza Bancorp
Subordinated Debentures
Fixed interest rate (as a percent)					7.125%
Number of subordinated notes assumed | note					3
Debt assumed in acquisition					$ 25,000,000
Redemption price (as a percent)					103.00%
Redemption price, subsequent reduction (as a percent)					0.50%