Share-Based Payment Arrangements (Narrative) (Details) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($) Entity $ / shares shares	Dec. 31, 2022 USD ($) $ / shares shares	Dec. 31, 2021 USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense recognized | $	$ 24.7	$ 23.5	$ 22.4
Recognized tax benefit related to share-based compensation | $	5.7	$ 7.0	$ 9.9
Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares, outstanding		1,476
Number of shares, exercisable		1,476
Weighted average exercise price | $ / shares		$ 53.73
Stock options exercised		7,630
Intrinsic value of options exercised | $		$ 0.1
Restricted and Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation expense | $	$ 45.6
Weighted-average period	2 years 10 months 24 days
Fair value of shares vested | $	$ 18.4	$ 16.9
Shares granted	652,461
Grant date fair value per share | $ / shares	$ 48.5
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	41,495
Grant date fair value per share | $ / shares	$ 51.14
Vesting performance period	3 years
Number of peer group regional banks | Entity	49
Performance Shares [Member] | Total Shareholder Return [Member] | Executive Management [Member] | Tranche One [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of maximum number of shares vested	200.00%
Performance Shares [Member] | Operating Earnings Per Share [Member] | Executive Management [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted	41,495
Grant date fair value per share | $ / shares	$ 46.73
Vesting performance period	2 years
2020 Long Term Incentive Plan [Member] | Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate awards authorized for grant	3,900,000
Maximum number of shares which may be granted to participant	250,000
Shares available for future issuance	2,000,000
2020 Long Term Incentive Plan [Member] | Options [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate awards authorized for grant	1,000,000