Loans Loans (Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period) (Details) - USD ($) $ in Thousands		Jul. 24, 2015	Jul. 17, 2015	Jul. 01, 2015	Jan. 16, 2015
North Bank
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Contractually required payments including interest				$ 8,563
Less: Nonaccretable difference				1,027
Cash flows expected to be collected	[1]			7,536
Less: Accretable yield				866
Fair value of PCI loans acquired				$ 6,670
Community Financial Shares, Inc.
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Contractually required payments including interest		$ 38,656
Less: Nonaccretable difference		4,437
Cash flows expected to be collected	[1]	34,219
Less: Accretable yield		2,895
Fair value of PCI loans acquired		$ 31,324
Suburban Illinois Bancorp
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Contractually required payments including interest			$ 95,804
Less: Nonaccretable difference			13,888
Cash flows expected to be collected	[1]		81,916
Less: Accretable yield			5,334
Fair value of PCI loans acquired			$ 76,582
Delavan Bancshares
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Contractually required payments including interest					$ 15,791
Less: Nonaccretable difference					1,442
Cash flows expected to be collected	[1]				14,349
Less: Accretable yield					898
Fair value of PCI loans acquired					$ 13,451

[1] Represents undiscounted expected principal and interest cash at acquisition.