Shareholders' Equity, Dividends Restrictions and Other Regulatory Matters (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($) vote shares	Dec. 31, 2014 USD ($) shares	Dec. 31, 2013 USD ($)
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Trust Preferred Securities included in Tier 1 capital	$ 32,100	$ 128,500
Capital required for common equity Tier 1 capital to risk-weighted assets	4.50%
Tier 1 Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets	6.00%
Capital Required for Capital Adequacy to Risk Weighted Assets	8.00%
Leverage Capital Required Ratio To Tangible Assets	4.00%
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	$ 6,000	$ 9,000
Subordinated Debt, Annual Tier 2 Discount Percentage	20.00%
Maximum Undivided Profits Elgible For Dividend Payment Without Changing Well Capitalized Status	$ 902,600
Average Required Maintence Of Non Interst Bearing Reserve Balance	$ 531,600
Capital Conservation Buffer, Annual Percentage Increase	0.625%
Capital Conservation Buffer	2.50%
Common Class A [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Votes per share of common stock | vote	1
Stock Repurchase Program, Number of Shares Authorized to be Repurchased | shares	100,000
Stock Repurchased During Period, Shares | shares		167,600
Class B Common Stock
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Votes per share of common stock | vote	16
Stock Repurchased and Retired During Period, Shares | shares	0	45,900
Parent
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Dividend Income, Banking Subsidiaries	$ 75,006	$ 82,419	$ 131,006
BancShares [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 Capital for Capital Adequacy	2,831,242	2,690,324
Capital Required for Capital Adequacy	3,140,212	2,904,123
Leverage Capital Required for Capital Adequacy	$ 2,831,242	$ 2,690,324
Tier 1 Risk Based Capital to Risk Weighted Assets	12.65%	13.61%
Capital to Risk Weighted Assets	14.03%	14.69%
Leverage Capital to Average Assets	8.96%	8.91%
Tier 1 Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets	8.00%	6.00%
Common equity Tier 1	$ 2,799,163
Common equity Tier 1 to risk-weighted assets	12.50965%
Common equity Tier 1 required to be well capitalized to risk-weighted assets	6.50%
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
Capital Required for Capital Adequacy		657,475
Leverage Capital Required for Capital Adequacy		$ 653,515
Tier 1 Risk Based Capital to Risk Weighted Assets		15.11%
Capital to Risk Weighted Assets		15.20%
Leverage Capital to Average Assets		7.89%
Tier 1 Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets		6.00%
Capital Required to be Well Capitalized		10.00%
Leverage Capital Required to be Well Capitalized to Average Assets		5.00%
FCB [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 Capital for Capital Adequacy	$ 2,821,475	$ 2,019,595
Capital Required for Capital Adequacy	3,038,070	2,212,163
Leverage Capital Required for Capital Adequacy	$ 2,821,475	$ 2,019,595
Tier 1 Risk Based Capital to Risk Weighted Assets	12.64%	13.12%
Capital to Risk Weighted Assets	13.61%	14.37%
Leverage Capital to Average Assets	8.95%	9.30%
Tier 1 Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets	8.00%	6.00%
Common equity Tier 1	$ 2,821,475
Common equity Tier 1 to risk-weighted assets	12.63988%
Common equity Tier 1 required to be well capitalized to risk-weighted assets	6.50%
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	$ 75,006	$ 30,000