Income Taxes (Details) - Deferred Tax Assets And Liabilities - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets:
Allowance for credit losses	$ 30,399	$ 26,131
Deferred gain on sale-leaseback transaction	28,133	0
Unrealized losses on securities	18,320	18,328
Non-equity based compensation	6,060	3,739
Equity based compensation	5,228	5,469
OREO	4,336	2,597
Federal and state net operating loss (NOL) carryforwards	388	7,679
Alternative minimum tax (AMT) and other credit carryforwards	90	17,739
Property valuation adjustments	0	3,003
Other	10,997	8,375
Total deferred tax assets	103,951	93,060
Deferred tax liabilities:
Acquisition adjustments	(13,407)	(9,371)
Accrued retirement benefits	(6,281)	(6,065)
Deferred loan fees and costs	(3,172)	(2,432)
Cancellation of indebtedness income	(2,136)	(3,204)
Other	(6,442)	(5,039)
Total deferred tax liabilities	(31,438)	(26,111)
Deferred tax valuation allowance	0	0
Net deferred tax assets	72,513	66,949
Tax effect of adjustments related to other comprehensive (loss) income	27,694	19,744
Net deferred tax assets including adjustments	100,207	86,693
NOL carryforwards available to offset future taxable income:
AMT credits	0	17,739
Internal Revenue Service (IRS)
NOL carryforwards available to offset future taxable income:
Gross NOL Carryforwards	574	922
Illinois
NOL carryforwards available to offset future taxable income:
Gross NOL Carryforwards	26,342	160,016
Indiana
NOL carryforwards available to offset future taxable income:
Gross NOL Carryforwards	$ 1,003	$ 11,796