Shareholders' Equity, Dividends Restrictions and Other Regulatory Matters (Details) (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets	4.00%
Capital Required for Capital Adequacy to Risk Weighted Assets	8.00%
Leverage Capital Required Ratio To Tangible Assets	3.00%
Trust Preferred Securities	$ 128,500,000fcnca_TrustPreferredSecurities
Percent Of Trust Preferred Securities Excluded From Tier One Starting In 2013	75.00%
Remaining Percent of Trust Preferred Securities Excluded from Tier One After 2015	25.00%
Tier 2 capital	9,000,000us-gaap_TierTwoRiskBasedCapital	25,000,000us-gaap_TierTwoRiskBasedCapital
Amount Available for Dividend Distribution without Prior Approval from Regulatory Agency	1,480,000,000
Maximum Undivided Profits Elgible For Dividend Payment Without Changing Well Capitalized Status	672,400,000
Average Required Maintence Of Non Interst Bearing Reserve Balance	382,700,000
Common Class A [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Votes per share of common stock	1
Stock Repurchase Program, Number of Shares Authorized to be Repurchased	100,000
Stock Repurchased During Period, Shares		1,973
Class B Common Stock
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Votes per share of common stock	16
Stock Repurchase Program, Number of Shares Authorized to be Repurchased	25,000
Stock Repurchased and Retired During Period, Shares	45,900
Parent
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Dividends from subsidiaries	82,419,000	131,006,000	179,588,000
BancShares [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 Capital for Capital Adequacy	2,690,324,000	2,103,926,000
Capital Required for Capital Adequacy	2,904,123,000	2,315,579,000
Leverage Capital Required for Capital Adequacy	2,690,324,000	2,103,926,000
Tier 1 Risk Based Capital to Risk Weighted Assets	13.61%	14.89%
Capital to Risk Weighted Assets	14.69%	16.39%
Leverage Capital to Average Assets	8.91%	9.80%
Tier 1 Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets	6.00%	6.00%
Capital Required to be Well Capitalized	10.00%	10.00%
Leverage Capital Required to be Well Capitalized to Average Assets	5.00%	5.00%
FCB-SC [Member] [Domain]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 Capital for Capital Adequacy	653,515,000	734,218,000
Capital Required for Capital Adequacy	657,475,000	787,962,000
Leverage Capital Required for Capital Adequacy	653,515,000	734,218,000
Tier 1 Risk Based Capital to Risk Weighted Assets	15.11%	17.09%
Capital to Risk Weighted Assets	15.20%	18.34%
Leverage Capital to Average Assets	7.89%	9.12%
Tier 1 Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets	6.00%	6.00%
Capital Required to be Well Capitalized	10.00%	10.00%
Leverage Capital Required to be Well Capitalized to Average Assets	5.00%	5.00%
FCB-SC [Member] [Domain] \| Parent
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Dividends from subsidiaries	52,397,000
FCB [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 Capital for Capital Adequacy	2,019,595,000	1,978,136,000
Capital Required for Capital Adequacy	2,212,163,000	2,179,248,000
Leverage Capital Required for Capital Adequacy	2,019,595,000	1,978,136,000
Tier 1 Risk Based Capital to Risk Weighted Assets	13.12%	14.10%
Capital to Risk Weighted Assets	14.37%	15.54%
Leverage Capital to Average Assets	9.30%	9.34%
Tier 1 Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets	6.00%	6.00%
Capital Required to be Well Capitalized	10.00%	10.00%
Leverage Capital Required to be Well Capitalized to Average Assets	5.00%	5.00%
FCB [Member] \| Parent
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Dividends from subsidiaries	$ 30,022,000	$ 131,006,000	$ 179,588,000

Average Required Maintenance of Noninterest-Bearing Reserve Balance

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Leverage Capital Required Ratio To Tangible Assets

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- Definition

Maximum Undivided Profits Elgible For Dividend Payment Without Changing Well Capitalized Status

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- Definition

Percent of Trust Preferred Securities Excluded from Tier One Starting In 2015

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Remaining Percent of Trust Preferred Securities Excluded from Tier One After 2015

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- Definition

The number of votes allowed for common stock dividends

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Trust Preferred Securities

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- Definition

The amount of total capital as defined in the regulations.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 948

-SubTopic 10

-Section 50

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- Definition

The minimum Total risk based capital ratio (total capital divided by risk weighted assets) required for capital adequacy purposes under the regulatory framework for prompt corrective action.

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The Total risk based capital ratio (total capital divided by risk weighted assets) required to be categorized as "well capitalized", in the regulatory framework for prompt corrective action.

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-Publisher FASB

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Total Capital divided by risk weighted assets as defined in the regulations.

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- Definition

Amount of operating dividend income on securities.

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-04.2)

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 2

-Article 9

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Amount of dividends that can be declared or paid without approval of regulatory agency.

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

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- Definition

Number of shares that have been repurchased and retired during the period.

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-Section 02

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Number of shares that have been repurchased during the period and have not been retired and are not held in treasury. Some state laws may govern the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

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The number of shares authorized to be repurchased by an entity's Board of Directors under a stock repurchase plan.

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- Definition

Tier 1 Leverage Capital as defined in the regulations. Also called Core Capital.

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The amount of Tier 1 Leverage Capital required to be categorized as well capitalized divided by average assets as defined in the regulatory framework for prompt corrective action.

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Tier 1 Leverage Capital divided by average assets as defined in the regulations.

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Tier 1 Risk Based Capital as defined in the regulations.

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The minimum Tier One Capital Ratio (Tier one capital divided by risk-weighted assets) required for capital adequacy purposes under the regulatory framework for prompt corrective action.

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The Tier 1 capital ratio (Tier 1 capital divided by risk weighted assets) required to be categorized as "well capitalized" under the regulatory framework for prompt corrective action.

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Tier 1 capital divided by risk weighted assets as defined by regulations.

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Tier 2 risk-based capital as defined in the regulations.

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