Regulatory Capital - Well Capitalized Regulatory Requirements (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Actual Amount
Tier 1 Capital (to Average Assets)	$ 3,264,309	$ 2,896,091
Tier 1 Capital (to Risk-Weighted Assets)	3,264,309	2,896,091
Total Capital (to Risk-Weighted Assets)	3,600,668	3,196,279
Tier 1 Capital (to Average Assets)	$ 3,264,309	$ 2,896,091
Actual Ratio
Tier 1 Capital (to Average Assets)	12.20%	12.10%
Tier 1 Capital (to Risk-Weighted Assets)	12.20%	12.10%
Total Capital (to Risk-Weighted Assets)	13.40%	13.30%
Tier 1 Capital (to Average Assets)	10.20%	11.10%
Well Capitalized Regulatory Requirements, Amount
Tier 1 Capital (to Average Assets)	$ 1,876,050	$ 1,528,209
Tier 1 Capital (to Risk-Weighted Assets)	2,278,060	1,887,787
Total Capital (to Risk-Weighted Assets)	2,814,074	2,367,226
Tier 1 Capital (to Average Assets)	$ 1,282,642	$ 1,039,226
Well Capitalized Regulatory Requirements, Ratio
Tier 1 Capital (to Average Assets)	7.00%	6.375%
Tier 1 Capital (to Risk-Weighted Assets)	8.50%	7.875%
Total Capital (to Risk-Weighted Assets)	10.50%	9.875%
Tier 1 Capital (to Average Assets)	4.00%	4.00%

Common Equity Tier One Risk Based Capital

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Tier One Common Equity Capital Required to be Well Capitalized to Risk Weighted Assets

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Tier One Common Equity Capital to Risk Weighted Assets

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Tier One Risk Based Capital for Common Equity Required to be Capitalized

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The amount of total capital as defined in the regulations.

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The amount of Total Capital required to be categorized as well as capitalized 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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Total Capital divided by risk weighted assets as defined in the regulations.

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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 under the regulatory framework for prompt corrective action.

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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 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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