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Business and Summary of Significant Accounting Policies - Cash and cash equivalents (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Business Description And Accounting Policies [Abstract]
Reserve requirement	$ 15.8	$ 14.1

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- Definition

Business description and accounting policies.

+ References

No definition available.

+ Details

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- Definition

Cash on hand or on deposit with the Federal Reserve Bank required to meet regulatory reserve and clearing requirements.

+ References

No definition available.

+ Details

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