Acquisition and Divestiture Activity - Schedule of Acquired Loan Data (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015
Tower Financial Corporation [Member]
Loans at Acquisition Date [Line Items]
Fair Value of Acquired Loans at Acquisition Date	$ 371,054
Tower Financial Corporation [Member] | Acquired Receivables Subject to ASC 310-30 [Member]
Loans at Acquisition Date [Line Items]
Fair Value of Acquired Loans at Acquisition Date	12,855
Gross Contractual Amounts Receivable at Acquisition Date	22,746
Best Estimate at Acquisition Date of Contractual Cash Flows Not Expected to be Collected	5,826
Tower Financial Corporation [Member] | Acquired Receivables Not Subject to ASC 310-30 [Member]
Loans at Acquisition Date [Line Items]
Fair Value of Acquired Loans at Acquisition Date	358,199
Gross Contractual Amounts Receivable at Acquisition Date	450,865
Best Estimate at Acquisition Date of Contractual Cash Flows Not Expected to be Collected	42,302
LSB Financial Corp. [Member]
Loans at Acquisition Date [Line Items]
Fair Value of Acquired Loans at Acquisition Date	236,607
LSB Financial Corp. [Member] | Acquired Receivables Subject to ASC 310-30 [Member]
Loans at Acquisition Date [Line Items]
Fair Value of Acquired Loans at Acquisition Date	11,986
Gross Contractual Amounts Receivable at Acquisition Date	24,493
Best Estimate at Acquisition Date of Contractual Cash Flows Not Expected to be Collected	9,903
LSB Financial Corp. [Member] | Acquired Receivables Not Subject to ASC 310-30 [Member]
Loans at Acquisition Date [Line Items]
Fair Value of Acquired Loans at Acquisition Date	224,621
Gross Contractual Amounts Receivable at Acquisition Date	340,832
Best Estimate at Acquisition Date of Contractual Cash Flows Not Expected to be Collected	57,884
United Bancorp, Inc. [Member]
Loans at Acquisition Date [Line Items]
Fair Value of Acquired Loans at Acquisition Date	632,016
United Bancorp, Inc. [Member] | Acquired Receivables Subject to ASC 310-30 [Member]
Loans at Acquisition Date [Line Items]
Fair Value of Acquired Loans at Acquisition Date	8,391
Gross Contractual Amounts Receivable at Acquisition Date	15,483
Best Estimate at Acquisition Date of Contractual Cash Flows Not Expected to be Collected	5,487
United Bancorp, Inc. [Member] | Acquired Receivables Not Subject to ASC 310-30 [Member]
Loans at Acquisition Date [Line Items]
Fair Value of Acquired Loans at Acquisition Date	623,625
Gross Contractual Amounts Receivable at Acquisition Date	798,967
Best Estimate at Acquisition Date of Contractual Cash Flows Not Expected to be Collected	89,430
Founders Financial Corporation [Member]
Loans at Acquisition Date [Line Items]
Fair Value of Acquired Loans at Acquisition Date	339,569
Founders Financial Corporation [Member] | Acquired Receivables Subject to ASC 310-30 [Member]
Loans at Acquisition Date [Line Items]
Fair Value of Acquired Loans at Acquisition Date	6,607
Gross Contractual Amounts Receivable at Acquisition Date	11,103
Best Estimate at Acquisition Date of Contractual Cash Flows Not Expected to be Collected	2,684
Founders Financial Corporation [Member] | Acquired Receivables Not Subject to ASC 310-30 [Member]
Loans at Acquisition Date [Line Items]
Fair Value of Acquired Loans at Acquisition Date	332,962
Gross Contractual Amounts Receivable at Acquisition Date	439,031
Best Estimate at Acquisition Date of Contractual Cash Flows Not Expected to be Collected	$ 61,113