Income Taxes (Detail) - Deferred Tax Assets And Liabilities (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012
Deferred tax assets:
Alternative minimum tax (AMT) and other credit carryforwards	$ 19,184		$ 13,379
Federal net operating loss (NOL) carryforwards	14,579		54,770
Allowance for credit losses	30,492		31,762
Unrealized losses on securities	21,374		23,737
OREO	6,541		4,949
State NOL carryforwards	15,859		17,287
Other	19,049		15,047
Total deferred tax assets	127,078		160,931
Deferred tax liabilities:
Purchase accounting adjustments and intangibles	(16,977)		(15,402)
Deferred loan fees	(1,984)		(2,565)
Accrued retirement benefits	(7,095)		(5,151)
FHLB stock dividends	(1,222)		(2,167)
Depreciation	(2,111)		(2,049)
Cancellation of indebtedness income	(5,340)		(5,340)
Other	(3,107)		(5,548)
Total deferred tax liabilities	(37,836)		(38,222)
Deferred tax valuation allowance	0		0
Net deferred tax assets	89,242		122,709
Tax effect of adjustments related to other comprehensive (loss) income	18,382		10,896
Net deferred tax assets including adjustments	107,624		133,605
Net operating loss carryforwards available to offset future taxable income:
Other credits	19,184	[1]	13,379	[1]
Internal Revenue Service (IRS)
Net operating loss carryforwards available to offset future taxable income:
Gross NOL Carryforwards	41,654		156,486
Illinois
Net operating loss carryforwards available to offset future taxable income:
Gross NOL Carryforwards	290,076		297,448
Indiana
Net operating loss carryforwards available to offset future taxable income:
Gross NOL Carryforwards	$ 16,112		$ 31,170

[1] Consists of AMT credits, which have an indefinite life, and other credits, which have a 20-year life. Approximately $3.1 million of other credits will begin to expire during the year ended December 31, 2028.