Acquisition and Divestiture Activity - Schedule of Components of Estimated Fair Value of Intangible Assets (Detail) - Founders Financial Corporation [Member] $ in Millions	3 Months Ended
Mar. 31, 2016 USD ($)
Core Deposit [Member]
Business Acquisition [Line Items]
Estimated Fair Value	$ 2.9
Estimated Useful Lives (Years)	7 years
Customer Trust Relationships [Member]
Business Acquisition [Line Items]
Estimated Fair Value	$ 2.6
Estimated Useful Lives (Years)	12 years

Weighted average amortization period of finite-lived intangible assets acquired either individually or as part of a group of assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=26713463&loc=d3e16265-109275

Name:	us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration