Basis of Accounting and Consolidation Basis of Accounting and Consolidation (Acquisitions) (Details)	Nov. 15, 2018 USD ($) $ / shares shares	May 01, 2018 USD ($) $ / shares shares	Mar. 31, 2019 USD ($) $ / shares	Dec. 31, 2018 USD ($) $ / shares
Agreement And Plan Of Merger [Abstract]
Common stock, par value (in dollars per share) | $ / shares			$ 4	$ 4
Assets | $			$ 3,895,619,000	$ 3,839,734,000
Gross loans | $			2,607,624,000	2,658,136,000
Deposits | $			$ 3,046,213,000	$ 2,988,686,000
First BancTrust [Member]
Agreement And Plan Of Merger [Abstract]
Percent Of Acquiree Outstanding Stock Being Acquired In Merger		1.00
Par Value Of Outstanding Stock Being Acquired In Merger | $ / shares		$ 0.01
Right To Receive Value of Cash Option | $ / shares		$ 5.00
Right To Receive Value Of Share Option | shares		0.800
Shares, Issued | shares		1,643,900
Shares Issued, Price Per Share | $ / shares		$ 37.32
Aggregate Total Of Cash Paid In Business Combination | $		$ 10,275,000
SCB Bancorp [Member]
Agreement And Plan Of Merger [Abstract]
Percent Of Acquiree Outstanding Stock Being Acquired In Merger	1.00
Par Value Of Outstanding Stock Being Acquired In Merger | $ / shares	$ 7.50
Right To Receive Value of Cash Option | $ / shares	$ 307.93
Right To Receive Value Of Share Option | shares	8.0228
Shares, Issued | shares	1,330,571
Aggregate Total Of Cash Paid In Business Combination | $	$ 19,046,000
Dividends, Cash | $	$ 25,000,000