Share-Based Payment Arrangements (Narrative) (Details) $ / shares in Units, $ in Millions	3 Months Ended
Mar. 31, 2019 USD ($) entity $ / shares shares	Mar. 31, 2018 USD ($)
Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercises of stock options	0
Intrinsic value of options exercised \| $		$ 0.5
Restricted and Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation expense \| $	$ 51.0
Weighted-average period	3 years 3 months 18 days
Total fair value of shares vested \| $	$ 0.1	$ 0.3
Shares granted	72,081,000
Grant date fair value per share \| $ / shares	$ 34.20
Performance Shares [Member] \| Executive Management [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Service period	3 years
Performance Shares [Member] \| Total Shareholder Return [Member] \| Executive Management [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted	33,691
Grant date fair value per share \| $ / shares	$ 35.27
Vesting performance period	3 years
Number of peer group regional banks \| entity	42
Percentage of maximum number of shares vested	200.00%
Performance Shares [Member] \| Core Earnings Per Share [Member] \| Executive Management [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted	33,691
Grant date fair value per share \| $ / shares	$ 32.15
Vesting performance period	2 years

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Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (i)
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Unrecognized cost of unvested share-based awards, other than options, awarded to employees as compensation.

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Estimated period over which an employee is required to provide service in exchange for the equity-based payment award, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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Percentage of vesting of share-based compensation awards.

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Number of share options (or share units) exercised during the current period.

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