Payable to FDIC for Loss Share Agreements

No definition available.

Name:	fcnca_PayableToFdicForLossShareAgreements
Namespace Prefix:	fcnca_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Recourse Period Maximum1

+ References

No definition available.

+ Details

Name:	fcnca_RecoursePeriodMaximum1
Namespace Prefix:	fcnca_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the liability related to investments in low income housing tax credits which is reflected in other liabilities on the Consolidated Balance Sheet.

+ References

No definition available.

+ Details

Name:	fcnca_UnfundedCommitmentforLowIncomeHousingTaxCredits
Namespace Prefix:	fcnca_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Carrying amount of receivable assets originating from the indemnification agreement with the Federal Deposit Insurance Corporation (FDIC), in which the FDIC is to partially cover losses.

+ References

No definition available.

+ Details

Name:	us-gaap_FDICIndemnificationAsset
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_GuaranteeObligationsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 460

-SubTopic 10

-Section 50

-Paragraph 4

-Subparagraph (b)(1)

-URI http://asc.fasb.org/extlink&oid=6851643&loc=d3e12069-110248

+ Details

Name:	us-gaap_GuaranteeObligationsMaximumExposure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of loss contingency liability.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14326-108349

+ Details

Name:	us-gaap_LossContingencyAccrualAtCarryingValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Unused amount of commitments to extend credit to customers.

+ References

No definition available.

+ Details

Name:	us-gaap_UnusedCommitmentsToExtendCredit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_GuaranteeObligationsByNatureAxis=fcnca_RecourseObligationOnMortgageLoansSoldMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_GuaranteeObligationsByNatureAxis=us-gaap_CommitmentsToExtendCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_GuaranteeObligationsByNatureAxis=us-gaap_StandbyLettersOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LossContingenciesByNatureOfContingencyAxis=us-gaap_ObligationToRepurchaseReceivablesSoldMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Commitments and Contingencies (Details) (USD $)	3 Months Ended
Commitments and Contingencies (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2013
Guarantor Obligations [Line Items]
FDIC Indemnification Asset	21,340,000us-gaap_FDICIndemnificationAsset	$ 28,701,000us-gaap_FDICIndemnificationAsset	$ 74,784,000us-gaap_FDICIndemnificationAsset	$ 93,397,000us-gaap_FDICIndemnificationAsset
FDIC loss share payable	118,645,000	116,535,000
Commitments to Extend Credit
Guarantor Obligations [Line Items]
Unused Commitments to Extend Credit	7,570,000,000	7,190,000,000
Affordable housing program obligation	22,600,000	16,800,000
Standby Letters of Credit
Guarantor Obligations [Line Items]
Guarantor obligations amount	75,000,000	77,400,000
Recourse Obligation on Mortgage Loans Sold
Guarantor Obligations [Line Items]
Recourse Period, Maximum1	120 days
Obligation to Repurchase Receivables Sold
Guarantor Obligations [Line Items]
Reserve for estimated losses arising from repurchase of loans	3,100,000	$ 3,200,000