Securities - Additional Information (Detail) $ in Thousands	Jun. 30, 2015 USD ($) Securities	Dec. 31, 2014 USD ($) Securities
Investments, Debt and Equity Securities [Abstract]
Number of securities holdings	0	0
Shareholders' equity percentage	10.00%	10.00%
Securities \| $	$ 344,036	$ 325,799

The fair value of trading securities that serve as collateral for borrowings.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=49124121&loc=d3e5086-111524

Name:	us-gaap_TradingSecuritiesPledgedAsCollateral
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant