Document And Entity Information - shares	9 Months Ended
	Sep. 30, 2018	Oct. 31, 2018
Entity Registrant Name	FIRST CITIZENS BANCSHARES INC /DE/
Entity Central Index Key	0000798941
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Document Type	10-Q
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q3
Amendment Flag	false
Class A Common Stock
Entity Common Stock, Shares Outstanding		10,805,220
Class B Common Stock
Entity Common Stock, Shares Outstanding		1,005,185