Acquisitions - Schedule of Purchase Price of Assets Acquired and Liabilities Assumed (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Sep. 01, 2017	Dec. 31, 2016	Nov. 07, 2016	Sep. 30, 2016	Aug. 31, 2016	Jul. 18, 2016	Jun. 01, 2016
ASSETS
Goodwill	$ 93,750		$ 76,941
Kosciusko Financial Inc [Member]
ASSETS
Cash and due from banks								$ 38,950
Investment securities, available for sale								1,191
Total loans								102,569
Premises and equipment, net								1,466
FHLB stock								582
Goodwill					$ 6,400	$ 6,900		6,443
Core deposit intangible								526
Interest receivable								636
Cash value of life insurance								2,745
Other assets								765
Total assets purchased								155,873
Common shares issued					14,470			14,470
Cash paid					8,513			8,513
Total estimated purchase price								22,983
Deposits
Non-interest bearing								27,871
NOW accounts								35,213
Savings and money market								26,953
Certificates of deposits								32,771
Total deposits								122,808
Borrowings								9,038
Interest payable								55
Other liabilities								989
Total liabilities assumed								132,890
Kosciusko Financial Inc [Member] | Residential Mortgage [Member]
ASSETS
Total loans								26,244
Kosciusko Financial Inc [Member] | Commercial [Member]
ASSETS
Total loans								70,006
Kosciusko Financial Inc [Member] | Consumer [Member]
ASSETS
Total loans								$ 6,319
LaPorte Bancorp Inc [Member]
ASSETS
Cash and due from banks							$ 154,849
Investment securities, available for sale							23,779
Total loans							312,906
Premises and equipment, net							6,022
FHLB stock							4,029
Goodwill							20,993
Core deposit intangible							2,514
Interest receivable							844
Cash value of life insurance							15,267
Other assets							8,334
Total assets purchased							549,537
Common shares issued					60,306		60,306
Cash paid					$ 38,328		38,328
Total estimated purchase price							98,634
Deposits
Non-interest bearing							66,733
NOW accounts							99,346
Savings and money market							117,688
Certificates of deposits							87,605
Total deposits							371,372
Borrowings							64,793
Interest payable							178
Subordinated debt							4,504
Other liabilities							10,056
Total liabilities assumed							450,903
LaPorte Bancorp Inc [Member] | Residential Mortgage [Member]
ASSETS
Total loans							42,603
LaPorte Bancorp Inc [Member] | Mortgage Warehousing [Member]
ASSETS
Total loans							99,752
LaPorte Bancorp Inc [Member] | Commercial [Member]
ASSETS
Total loans							153,750
LaPorte Bancorp Inc [Member] | Consumer [Member]
ASSETS
Total loans							$ 16,801
Central National Bank & Trust [Member]
ASSETS
Cash and due from banks				$ 27,860
Investment securities, available for sale				16,393
Total loans				10,470
Premises and equipment, net				444
FHLB stock				50
Goodwill				609
Core deposit intangible				190
Interest receivable				154
Other assets				49
Total assets purchased				56,219
Cash paid				5,311
Total estimated purchase price				5,311
Deposits
Non-interest bearing				24,079
NOW accounts				9,038
Savings and money market				13,829
Certificates of deposits				3,342
Total deposits				50,288
Borrowings				459
Interest payable				7
Other liabilities				154
Total liabilities assumed				50,908
Central National Bank & Trust [Member] | Residential Mortgage [Member]
ASSETS
Total loans				6,624
Central National Bank & Trust [Member] | Commercial [Member]
ASSETS
Total loans				2,267
Central National Bank & Trust [Member] | Consumer [Member]
ASSETS
Total loans				$ 1,579
Lafayette Community Bancorp [Member]
ASSETS
Cash and due from banks		$ 24,846
Investment securities, available for sale		6
Total loans		134,353
Premises and equipment, net		7,818
FHLB stock		395
Goodwill		16,106
Core deposit intangible		777
Interest receivable		338
Other assets		2,020
Total assets purchased		186,659
Common shares issued	30,108	30,108
Cash paid	$ 4,421	4,421
Total estimated purchase price		34,529
Deposits
Non-interest bearing		34,990
NOW accounts		30,174
Savings and money market		53,663
Certificates of deposits		32,271
Total deposits		151,098
Interest payable		42
Other liabilities		990
Total liabilities assumed		152,130
Lafayette Community Bancorp [Member] | Residential Mortgage [Member]
ASSETS
Total loans		30,997
Lafayette Community Bancorp [Member] | Commercial [Member]
ASSETS
Total loans		98,011
Lafayette Community Bancorp [Member] | Consumer [Member]
ASSETS
Total loans		$ 5,345