Loans (Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period) (Details) - USD ($) $ in Thousands		Dec. 31, 2015	[1]	Jul. 24, 2015	Jul. 17, 2015	Jul. 01, 2015	Jan. 16, 2015	Dec. 31, 2014	[1]	Dec. 31, 2013
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Less: Accretable yield		$ 63,902						$ 79,102		$ 115,909
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	[2]					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	[2]			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	[2]				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	[2]						14,349
Less: Accretable yield							898
Fair value of PCI loans acquired							$ 13,451

[1] As of December 31, 2015, the Company estimates that the remaining accretable yield balance to be amortized to the indemnification asset for the bank acquisitions is $6.6 million. The remainder of the accretable yield related to bank acquisitions is expected to be amortized to interest income.

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