Acquisitions Activity for Acquired Loans (Details) - USD ($) $ in Thousands				12 Months Ended
		May. 31, 2015	Apr. 01, 2015	Dec. 31, 2015	Dec. 31, 2014
Activity for accretable yield includes contractually due interest of acquired loans
Balance at beginning of year				$ 137,961	$ 32,610
Accretable yield added during the year from acquisitions				228,160	110,003
Accretable Yield Additions, Net of Reductions	[1]			(8,450)	3,806
Accretion recognized into interest income				(59,414)	(18,458)
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield, Reclassifications from Nonaccretable Difference				0	10,000
Balance at end of year				298,257	137,961
Lake Michigan Financial Corp [Member]
Activity for accretable yield includes contractually due interest of acquired loans
Balance at beginning of year				0
Accretable yield added during the year from acquisitions		$ 190,200		190,246
Accretable Yield Additions, Net of Reductions	[1]			(12,991)
Accretion recognized into interest income				(24,256)
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield, Reclassifications from Nonaccretable Difference				0
Balance at end of year				152,999	0
Monarch Community Bancorp [Member]
Activity for accretable yield includes contractually due interest of acquired loans
Balance at beginning of year				0
Accretable yield added during the year from acquisitions			$ 37,900	37,914
Accretable Yield Additions, Net of Reductions	[1]			1,336
Accretion recognized into interest income				(4,692)
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield, Reclassifications from Nonaccretable Difference				0
Balance at end of year				34,558	0
Northwestern Bancorp [Member]
Activity for accretable yield includes contractually due interest of acquired loans
Balance at beginning of year				104,675	0
Accretable yield added during the year from acquisitions				0	110,003
Accretable Yield Additions, Net of Reductions	[1]			(3,396)	(1,605)
Accretion recognized into interest income				(18,656)	(3,723)
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield, Reclassifications from Nonaccretable Difference				0	0
Balance at end of year				82,623	104,675
OAK [Member]
Activity for accretable yield includes contractually due interest of acquired loans
Balance at beginning of year				33,286	32,610
Accretable yield added during the year from acquisitions				0	0
Accretable Yield Additions, Net of Reductions	[1]			6,601	5,411
Accretion recognized into interest income				(11,810)	(14,735)
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield, Reclassifications from Nonaccretable Difference				0	10,000
Balance at end of year				$ 28,077	$ 33,286

[1] Represents additions in estimated contractual interest expected to be collected from acquired loans being renewed or extended, less reductions in contractual interest resulting from the early payoff of acquired loans.