Accounting for Certain Loans Acquired in a Transfer - Accretable Yield or Income Expected to be Collected (Detail) (Loans Purchased With Evidence Of Credit Deterioration [Member], USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance at January 1	$ 3,185	$ 6,111
Additions	1,758
Accretion	(288)	(451)
Reclassification from nonaccreatable difference
Disposals	(95)	(696)
Balance at June 30	4,560	4,964
Heartland [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance at January 1	3,185	6,111
Additions
Accretion	(288)	(451)
Reclassification from nonaccreatable difference
Disposals	(95)	(696)
Balance at June 30	2,802	4,964
Summit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance at January 1	494
Additions	1,758
Accretion
Reclassification from nonaccreatable difference
Disposals
Balance at June 30	$ 1,758