Business Combinations - Summary of Consideration Paid and Fair Value of Identifiable Assets Acquired and Liabilities Assumed (Parenthetical) (Detail) - shares	Oct. 09, 2015	Mar. 02, 2015
Alliance Bancorp, Inc. [Member] \| Pennsylvania [Member]
Business Acquisition [Line Items]
Common stock shares issued	2,459,120	2,459,120

Number of shares of equity interests issued or issuable to acquire entity.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (b)(4)
-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479

Name:	us-gaap_BusinessAcquisitionEquityInterestsIssuedOrIssuableNumberOfSharesIssued
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration