Mergers and Acquisitions (Activity for Acquired Loans) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Activity for accretable yield includes contractually due interest of acquired loans
Balance at beginning of period	$ 298,257	$ 137,961
Additions attributable to acquisitions	862,127	228,160
Additions (reductions)	(11,354)	(8,450)
Accretion recognized in interest income	(131,559)	(59,414)
Reclassification from nonaccretable difference	22,500
Balance at end of period	1,039,971	298,257
Talmer
Activity for accretable yield includes contractually due interest of acquired loans
Balance at beginning of period	0	0
Additions attributable to acquisitions	862,127	0
Additions (reductions)	0	0
Accretion recognized in interest income	(63,917)	0
Reclassification from nonaccretable difference	0
Balance at end of period	798,210	0
Lake Michigan
Activity for accretable yield includes contractually due interest of acquired loans
Balance at beginning of period	152,999	0
Additions attributable to acquisitions	0	190,246
Additions (reductions)	(3,552)	(12,991)
Accretion recognized in interest income	(33,031)	(24,256)
Reclassification from nonaccretable difference	5,000
Balance at end of period	121,416	152,999
Monarch
Activity for accretable yield includes contractually due interest of acquired loans
Balance at beginning of period	34,558	0
Additions attributable to acquisitions	0	37,914
Additions (reductions)	(1,908)	1,336
Accretion recognized in interest income	(5,468)	(4,692)
Reclassification from nonaccretable difference	0
Balance at end of period	27,182	34,558
Northwestern
Activity for accretable yield includes contractually due interest of acquired loans
Balance at beginning of period	82,623	104,675
Additions attributable to acquisitions	0	0
Additions (reductions)	(6,985)	(3,396)
Accretion recognized in interest income	(15,791)	(18,656)
Reclassification from nonaccretable difference	10,000
Balance at end of period	69,847	82,623
OAK
Activity for accretable yield includes contractually due interest of acquired loans
Balance at beginning of period	28,077	33,286
Additions attributable to acquisitions	0	0
Additions (reductions)	1,091	6,601
Accretion recognized in interest income	(13,352)	(11,810)
Reclassification from nonaccretable difference	7,500
Balance at end of period	$ 23,316	$ 28,077