| Cover | 12 Months Ended |
| Dec. 31, 2022 | |
| Document Information [Line Items] | |
| Document Type | DEF 14A |
| Amendment Flag | false |
| Entity Information [Line Items] | |
| Entity Registrant Name | FIRST CITIZENS BANCSHARES, INC. |
| Entity Central Index Key | 0000798941 |
| Pay vs Performance Disclosure - USD ($) | 12 Months Ended | ||
| Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020 | |
| Pay vs Performance Disclosure [Table] | |||
| Pay vs Performance [Table Text Block] | P AY ERSUS ERFORMANCE Year Summary Compensation Table Total for PEO (1) Compensation Actually Paid to PEO (2) Average Non-PEO Named Officers (3) Average Non-PEO Named Executive Officers (4) Value of Initial Fixed $100 Investment Based On: Net Income (7) ( in millions ) Total Return (5) Peer Group Return (6) 2022 $ 8,031,975 $ 8,031,975 $ 6,460,948 $ 5,982,322 $ 144 $ 98 $ 1,098 2021 5,629,478 5,686,151 2,868,125 2,901,866 157 124 547 2020 4,436,450 3,938,276 2,397,694 2,119,384 109 90 492 (1) XECUTIVE OMPENSATION (2) For each year, reflects the amount of “Compensation Actually Paid” to our Chief Executive Officer, Frank B. Holding, Jr., as computed in accordance with Item 402(v) of Regulation S-K. Year Reported Summary Total for PEO Reported Change in Present Value of Pension Benefits (a) Pension Benefit Adjustments (b) Compensation Actually Paid to PEO 2022 $ 8,031,975 $ -0- $ -0- $ 8,031,975 2021 5,629,478 (60,063 ) 116,736 5,686,151 2020 4,436,450 (581,100 ) 82,926 3,938,276 (a) Reflects subtraction of the aggregate change in the actuarial present value of Mr. Holding’s accumulated benefits under all defined benefit and actuarial pension plans as reported for him in the “Change in Pension Value and Nonqualified Deferred Compensation Earnings” column of the Summary Compensation Table for each year. (b) | ||
| Named Executive Officers, Footnote [Text Block] | For each year, reflects the total compensation amount reported for our Chief Executive Officer (our “PEO”), Frank B. Holding, Jr., in the “Total” column of our Summary Compensation Table that appears under the heading “E XECUTIVE OMPENSATION | ||
| Peer Group Issuers, Footnote [Text Block] | |||
| PEO Total Compensation Amount | $ 8,031,975 | $ 5,629,478 | $ 4,436,450 |
| PEO Actually Paid Compensation Amount | $ 8,031,975 | 5,686,151 | 3,938,276 |
| Adjustment To PEO Compensation, Footnote [Text Block] | For each year, reflects the amount of “Compensation Actually Paid” to our Chief Executive Officer, Frank B. Holding, Jr., as computed in accordance with Item 402(v) of Regulation S-K. Year Reported Summary Total for PEO Reported Change in Present Value of Pension Benefits (a) Pension Benefit Adjustments (b) Compensation Actually Paid to PEO 2022 $ 8,031,975 $ -0- $ -0- $ 8,031,975 2021 5,629,478 (60,063 ) 116,736 5,686,151 2020 4,436,450 (581,100 ) 82,926 3,938,276 (a) Reflects subtraction of the aggregate change in the actuarial present value of Mr. Holding’s accumulated benefits under all defined benefit and actuarial pension plans as reported for him in the “Change in Pension Value and Nonqualified Deferred Compensation Earnings” column of the Summary Compensation Table for each year. (b) | ||
| Non-PEO NEO Average Total Compensation Amount | $ 6,460,948 | 2,868,125 | 2,397,694 |
| Non-PEO NEO Average Compensation Actually Paid Amount | $ 5,982,322 | 2,901,866 | 2,119,384 |
| Adjustment to Non-PEO NEO Compensation Footnote [Text Block] | For each year, reflects the average of the amounts of “Compensation Actually Paid” to the other NEOs as a group (excluding Mr. Holding), as computed in accordance with Item 402(v) of Regulation S-K. In accordance with the requirements of Item 402(v), the following adjustments were made to average total compensation of the other NEOs as a group for each year to determine the “Compensation Actually Paid.” Year Average Non-PEO NEOs Average Equity Awards (a) Average Average Present Pension Average Pension Benefit Adjustments (d) Average Compensation Actually Paid to Non-PEO NEOs 2022 $ 6,460,948 $ (659,436 ) $ 148,923 $ -0- $ 31,887 $ 5,982,322 2021 2,868,125 -0- -0- ( 21,516 ) 55,257 2,901,866 2020 2,397,694 -0- -0- (323,938 ) 45,628 2,119,384 (a) For 2022, reflects subtraction of the average for our NEOs as a group (excluding Mr. Holding) of the fair value, computed in accordance with FASB ASC Topic 718, of equity awards granted during that year. The RSUs deemed to have been granted to Mrs. Alemany during 2022 upon conversion of an equity award previously granted to her by CIT, as described above under the Grants of Plan-Based Awards table, is the only equity award that is deemed to have been granted to any of our NEOs during 2022, 2021 or 2020. (b) | ||
| Compensation Actually Paid vs. Net Income [Text Block] | The for C OMPENSATION CTUALLY AID VS ET NCOME | ||
| Total Shareholder Return Vs Peer Group [Text Block] | The NEOs C OMPENSATION CTUALLY AID VS OMPANY AND EER ROUP | ||
| Total Shareholder Return Amount | $ 144 | 157 | 109 |
| Peer Group Total Shareholder Return Amount | 98 | 124 | 90 |
| Net Income (Loss) | $ 1,098,000,000 | 547,000,000 | 492,000,000 |
| PEO Name | Frank B. Holding, Jr. | ||
| PEO [Member] | Reported Change in Actuarial Present Value of Pension Benefits [Member] | |||
| Pay vs Performance Disclosure [Table] | |||
| Adjustment to Compensation Amount | $ 0 | (60,063) | (581,100) |
| PEO [Member] | Pension Benefit Adjustments [Member] | |||
| Pay vs Performance Disclosure [Table] | |||
| Adjustment to Compensation Amount | 0 | 116,736 | 82,926 |
| Non-PEO NEO [Member] | Average Reported Value of Equity Awards [Member] | |||
| Pay vs Performance Disclosure [Table] | |||
| Adjustment to Compensation Amount | (659,436) | 0 | 0 |
| Non-PEO NEO [Member] | Average Equity Award Adjustments [Member] | |||
| Pay vs Performance Disclosure [Table] | |||
| Adjustment to Compensation Amount | 148,923 | 0 | 0 |
| Non-PEO NEO [Member] | Average Reported Change in Actuarial Present Value of Pension Benefits [Member] | |||
| Pay vs Performance Disclosure [Table] | |||
| Adjustment to Compensation Amount | 0 | (21,516) | (323,938) |
| Non-PEO NEO [Member] | Average Pension Benefit Adjustments [Member] | |||
| Pay vs Performance Disclosure [Table] | |||
| Adjustment to Compensation Amount | $ 31,887 | $ 55,257 | $ 45,628 |
