Document And Entity Information - shares	6 Months Ended
	Jun. 30, 2019	Aug. 05, 2019
Entity Central Index Key	0000798941
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
Amendment Flag	false
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2019
Document Transition Report	false
Entity File Number	001-16715
Entity Registrant Name	First Citizens BancShares Inc /DE/
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	56-1528994
Entity Address, Address Line One	4300 Six Forks Road
Entity Address, City or Town	Raleigh
Entity Address, State or Province	NC
Entity Address, Postal Zip Code	27609
City Area Code	(919)
Local Phone Number	716-7000
Title of 12(b) Security	Class A Common Stock, Par Value $1
Trading Symbol	FCNCA
Security Exchange Name	NASDAQ
Title of 12(g) Security	Class B Common Stock, Par Value $1
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Class A Common Stock
Entity Common Stock, Shares Outstanding		10,105,120
Class B Common Stock
Entity Common Stock, Shares Outstanding		1,005,185