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Shareholders' Equity, Dividends Restrictions and Other Regulatory Matters (Details) $ in Thousands | 12 Months Ended
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Dec. 31, 2016 USD ($) vote shares | Dec. 31, 2015 USD ($) shares | Dec. 31, 2014 USD ($)
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] |  |  |
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 | $ 3,000 | $ 6,000 |
Subordinated Debt, Annual Tier 2 Discount Percentage | 20.00% |  |
Maximum Undivided Profits Elgible For Dividend Payment Without Changing Well Capitalized Status | $ 928,700 |  |
Average Required Maintence Of Non Interst Bearing Reserve Balance | $ 575,700 |  |
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 | 200,000 |  |
Stock Repurchased During Period, Shares | shares |  | 0 |
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 | 0 |
Parent |  |  |
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] |  |  |
Dividends from subsidiaries | $ 90,055 | $ 75,006 | $ 30,000
BancShares [Member] |  |  |
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] |  |  |
Tier 1 Capital for Capital Adequacy | 2,995,557 | 2,831,242 |
Capital Required for Capital Adequacy | 3,339,986 | 3,140,212 |
Leverage Capital Required for Capital Adequacy | $ 2,995,557 | $ 2,831,242 |
Tier 1 Risk Based Capital to Risk Weighted Assets | 12.42% | 12.65% |
Capital to Risk Weighted Assets | 13.85% | 14.03% |
Leverage Capital to Average Assets | 9.05% | 8.96% |
Tier 1 Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets | 8.00% | 8.00% |
Common equity Tier 1 | $ 2,995,557 | $ 2,799,163 |
Common equity Tier 1 to risk-weighted assets | 12.42294% | 12.50965% |
Common equity Tier 1 required to be well capitalized to risk-weighted assets | 6.50% | 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% |
Capital Conservation Buffer | 5.85% |  |
FCB [Member] |  |  |
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] |  |  |
Tier 1 Capital for Capital Adequacy | $ 2,942,829 | $ 2,821,475 |
Capital Required for Capital Adequacy | 3,172,757 | 3,038,070 |
Leverage Capital Required for Capital Adequacy | $ 2,942,829 | $ 2,821,475 |
Tier 1 Risk Based Capital to Risk Weighted Assets | 12.25% | 12.64% |
Capital to Risk Weighted Assets | 13.21% | 13.61% |
Leverage Capital to Average Assets | 8.94% | 8.95% |
Tier 1 Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets | 8.00% | 8.00% |
Common equity Tier 1 | $ 2,942,829 | $ 2,821,475 |
Common equity Tier 1 to risk-weighted assets | 12.25305% | 12.63988% |
Common equity Tier 1 required to be well capitalized to risk-weighted assets | 6.50% | 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% |
Capital Conservation Buffer | 5.21% |  |

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