Loans (Schedule of Aging of Recorded Investment in Loans) (Details) - USD ($) $ in Thousands	Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	$ 2,154,502	[1]	$ 2,001,415	[2]
Total Past Due	11,975	[1]	9,435	[2]
Loans Not Past Due	2,142,527	[1]	1,991,980	[2]
Accrued interest receivable included in total recorded investment in loans and leases	9,483		8,011
Commercial and Industrial Loans and Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	488,058	[1]	458,538	[2]
Total Past Due	2,479		101
Loans Not Past Due	485,579		458,437
Commercial Real Estate Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	929,040	[1]	858,030	[2]
Total Past Due	3,556		1,860
Loans Not Past Due	925,484		856,170
Agricultural Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	337,801	[1]	306,946	[2]
Total Past Due	295		744
Loans Not Past Due	337,506		306,202
Home Equity Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	152,757	[1]	134,032	[2]
Total Past Due	658		796
Loans Not Past Due	152,099		133,236
Consumer Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	67,647	[1]	60,099	[2]
Total Past Due	629		407
Loans Not Past Due	67,018		59,692
Residential Mortgage Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	179,199	[1]	183,770	[2]
Total Past Due	4,358		5,527
Loans Not Past Due	174,841		178,243
30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	4,927	[1]	5,965	[2]
30-59 Days Past Due | Commercial and Industrial Loans and Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	209		20
30-59 Days Past Due | Commercial Real Estate Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,229		1,509
30-59 Days Past Due | Agricultural Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	27		84
30-59 Days Past Due | Home Equity Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	366		707
30-59 Days Past Due | Consumer Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	246		175
30-59 Days Past Due | Residential Mortgage Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	2,850		3,470
60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	4,452	[1]	1,489	[2]
60-89 Days Past Due | Commercial and Industrial Loans and Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,365		4
60-89 Days Past Due | Commercial Real Estate Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,650		21
60-89 Days Past Due | Agricultural Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0		50
60-89 Days Past Due | Home Equity Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	93		16
60-89 Days Past Due | Consumer Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	97		147
60-89 Days Past Due | Residential Mortgage Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,247		1,251
90 Days or More Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	2,596	[1]	1,981	[2]
90 Days or More Past Due | Commercial and Industrial Loans and Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	905		77
90 Days or More Past Due | Commercial Real Estate Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	677		330
90 Days or More Past Due | Agricultural Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	268		610
90 Days or More Past Due | Home Equity Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	199		73
90 Days or More Past Due | Consumer Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	286		85
90 Days or More Past Due | Residential Mortgage Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	261		806
Loans Acquired with Deteriorated Credit Quality
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	9,117		11,048		$ 7,555
Total Past Due	443		757
Loans Not Past Due	8,674		10,291
Loans Acquired with Deteriorated Credit Quality | Commercial and Industrial Loans and Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	988		1,656		1,325
Loans Acquired with Deteriorated Credit Quality | Commercial Real Estate Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	6,452		7,688		5,363
Loans Acquired with Deteriorated Credit Quality | Agricultural Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	789		706		0
Loans Acquired with Deteriorated Credit Quality | Home Equity Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	0		0
Loans Acquired with Deteriorated Credit Quality | Consumer Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	0		53		0
Loans Acquired with Deteriorated Credit Quality | Residential Mortgage Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	888		945		$ 867
Loans Acquired with Deteriorated Credit Quality | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	342		130
Loans Acquired with Deteriorated Credit Quality | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	74		0
Loans Acquired with Deteriorated Credit Quality | 90 Days or More Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 27		627
Loans Acquired with Deteriorated Credit Quality | River Valley Bancorp
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total			262,809
Total Past Due			4,740
Loans Not Past Due			258,069
Loans Acquired with Deteriorated Credit Quality | River Valley Bancorp | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due			2,752
Loans Acquired with Deteriorated Credit Quality | River Valley Bancorp | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due			862
Loans Acquired with Deteriorated Credit Quality | River Valley Bancorp | 90 Days or More Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due			$ 1,126

[1] Total recorded investment in loans includes $9,483 in accrued interest.

[2] Total recorded investment in loans includes $8,011 in accrued interest.