Acquisitions (Activity for Acquired Loans) (Details) - USD ($) $ in Thousands					6 Months Ended
		May. 31, 2015	Apr. 01, 2015	Oct. 31, 2014	Jun. 30, 2015	Jun. 30, 2014
Activity for accretable yield includes contractually due interest of acquired loans
Balance at beginning of period					$ 137,961
Additions attributable to acquisitions					228,160
Accretable Yield Additions, Net of Reductions	[1]				2,765
Accretion recognized in interest income					(20,838)
Reclassification from nonaccretable difference					0
Balance at end of period					348,048
Northwestern Bancorp [Member]
Activity for accretable yield includes contractually due interest of acquired loans
Balance at beginning of period					104,675
Additions attributable to acquisitions				$ 110,000	0
Accretable Yield Additions, Net of Reductions	[1]				(2,859)
Accretion recognized in interest income					(10,058)
Reclassification from nonaccretable difference					0
Balance at end of period					91,758
OAK [Member]
Activity for accretable yield includes contractually due interest of acquired loans
Balance at beginning of period					33,286	$ 32,610
Additions attributable to acquisitions					0	0
Accretable Yield Additions, Net of Reductions	[1]				5,215	2,333
Accretion recognized in interest income					(6,326)	(7,594)
Reclassification from nonaccretable difference					0	10,000
Balance at end of period					32,175	$ 37,349
Lake Michigan Financial Corp [Member]
Activity for accretable yield includes contractually due interest of acquired loans
Balance at beginning of period					0
Additions attributable to acquisitions		$ 190,246			190,246
Accretable Yield Additions, Net of Reductions	[1]				1,550
Accretion recognized in interest income					(3,486)
Reclassification from nonaccretable difference					0
Balance at end of period					188,310
Monarch Community Bancorp [Member]
Activity for accretable yield includes contractually due interest of acquired loans
Balance at beginning of period					0
Additions attributable to acquisitions			$ 37,914		37,914
Accretable Yield Additions, Net of Reductions	[1]				(1,141)
Accretion recognized in interest income					(968)
Reclassification from nonaccretable difference					0
Balance at end of period					$ 35,805

[1] Represents additions of 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.