Loans - Activity for Accretable Yield (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Activity for accretable yield
Balance at beginning of period	$ 1,038,219	$ 256,540	$ 1,039,971	$ 298,257
Addition attributable to acquisitions		862,127		862,127
Accretion recognized in interest income	(60,403)	(34,018)	(183,804)	(68,458)
Net reclassification (to) from nonaccretable difference	(1,812)	7,224	119,837	(53)
Balance at end of period	976,004	1,091,873	976,004	1,091,873
Talmer
Activity for accretable yield
Balance at beginning of period	801,369	0	798,210	0
Addition attributable to acquisitions		862,127		862,127
Accretion recognized in interest income	(43,816)	(17,415)	(133,478)	(17,415)
Net reclassification (to) from nonaccretable difference	11,861	0	104,682	0
Balance at end of period	769,414	844,712	769,414	844,712
Lake Michigan
Activity for accretable yield
Balance at beginning of period	121,572	125,343	121,416	152,999
Addition attributable to acquisitions		0		0
Accretion recognized in interest income	(7,201)	(7,968)	(22,050)	(25,259)
Net reclassification (to) from nonaccretable difference	(14,482)	6,565	523	(3,800)
Balance at end of period	99,889	123,940	99,889	123,940
Monarch
Activity for accretable yield
Balance at beginning of period	24,270	30,859	27,182	34,558
Addition attributable to acquisitions		0		0
Accretion recognized in interest income	(1,119)	(1,322)	(3,459)	(4,158)
Net reclassification (to) from nonaccretable difference	168	114	(404)	(749)
Balance at end of period	23,319	29,651	23,319	29,651
North-western
Activity for accretable yield
Balance at beginning of period	71,212	73,746	69,847	82,623
Addition attributable to acquisitions		0		0
Accretion recognized in interest income	(5,263)	(3,890)	(15,222)	(11,919)
Net reclassification (to) from nonaccretable difference	(1,358)	526	9,966	(322)
Balance at end of period	64,591	70,382	64,591	70,382
OAK
Activity for accretable yield
Balance at beginning of period	19,796	26,592	23,316	28,077
Addition attributable to acquisitions		0		0
Accretion recognized in interest income	(3,004)	(3,423)	(9,595)	(9,707)
Net reclassification (to) from nonaccretable difference	1,999	19	5,070	4,818
Balance at end of period	$ 18,791	$ 23,188	$ 18,791	$ 23,188

The aggregate excess of a loan's cash flows expected to be collected over the investor's initial investment in the loan for loans accounted for as debt securities, with evidence of deterioration of credit quality since origination that were acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 15
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82894507&loc=d3e13503-111538

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=82894903&loc=d3e15032-111544

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- Definition

Current period recognition due to accretion of the excess of a loan's cash flows expected to be collected over the investor's initial investment in the loan for loans accounted for as debt securities, with evidence of deterioration of credit quality since origination that were acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable.

+ References

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- Definition

Increases in the aggregate excess of a loan's cash flows expected to be collected over the investor's initial investment in the loan due to the acquisition of similar loans accounted for as debt securities during the period. This relates to loans accounted for as debt securities, with evidence of deterioration of credit quality since origination that were acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=82894903&loc=d3e15032-111544

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 15
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82894507&loc=d3e13503-111538

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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No definition available.

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- Definition

Change in the estimate of cash flows expected to be collected, after acquisition of a loan, which results in an increase in accretable yield (for example, if actual cash flows are significantly greater than previously expected). This relates to loans accounted for as debt securities, with evidence of deterioration of credit quality since origination that was acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable.

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