Regulatory Matters (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Compliance With Regulatory Capital Requirements Under Banking Regulations [Line Items]
Cash dividends paid to parent Company by consolidated subsidiaries	$ 139.0	$ 111.0	$ 122.0
Amount available to be paid as dividends without prior regulatory approval	$ 542.0
Minimum ratio of qualifying total capital to risk-weighted assets (ratio)	8.00%
Common Equity Tier 1 capital required for capital adequacy to risk weighted assets (ratio)	4.50%
Tier 1 risk based capital required for capital adequacy to risk weighted assets (ratio)	6.00%
Tier 1 leverage capital required for capital adequacy to average assets (ratio)	4.00%
Ratio required for banks to be well capitalized, total capital to risk-weighted assets	10.00%
Ratio required for banks to be well capitalized, Tier 1 capital to risk-weighted assets	8.00%
Ratio required for banks to be well capitalized, Common Equity Tier 1 capital risk weighted assets	6.50%
Ratio required for banks to be well capitalized, Tier 1 leverage ratio	5.00%
Federal Reserve Bank
Compliance With Regulatory Capital Requirements Under Banking Regulations [Line Items]
Cash reserve requirement	$ 750.0	$ 611.1

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

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The minimum amount of Tier 1 Leverage Capital for capital adequacy purposes divided by average assets as defined in the regulations.

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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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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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Cash Reserve Requirement

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Common Equity Tier One Capital Required for Capital Adequacy to Risk Weighted Assets

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