Cover Page - shares	3 Months Ended
	Mar. 31, 2021	Apr. 30, 2021
Cover [Abstract]
Document Type	10-Q
Document Transition Report	false
Document Period End Date	Mar. 31, 2021
Entity File Number	001-36408
Entity Registrant Name	PACWEST BANCORP
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	33-0885320
Entity Address, Address Line One	9701 Wilshire Blvd., Suite 700
Entity Address, City or Town	Beverly Hills
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	90212
City Area Code	310
Local Phone Number	887-8500
Title of 12(b) Security	Common Stock, par value $0.01 per share
Trading Symbol	PACW
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Central Index Key	0001102112
Entity Filer Category	Large Accelerated Filer
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Interactive Data Current	Yes
Document Quarterly Report	true
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		116,916,461