Sum of the carrying amounts as of the date of the latest financial statement presented of securities which are owned but transferred to another party to serve as collateral to partially or fully secure a debt obligation, repurchase agreement or other current or potential obligation, and for which the transferee is not permitted to sell or re-pledge them to an unrelated party.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 1A
-Subparagraph (b)(1)(i)
-URI http://asc.fasb.org/extlink&oid=64858031&loc=SL6224234-111729

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

Derivatives - Additional Information (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($) Derivative	Mar. 31, 2017 USD ($)	Dec. 31, 2017 USD ($)
Derivative [Line Items]
Carrying value of pledged securities	$ 928,800		$ 834,900
Risk participation agreements entered into \| Derivative	3
Proceeds from sale of risk participation agreement	$ 35,000
Interest Rate Swap
Derivative [Line Items]
Carrying value of pledged securities	2,900
ERROR in label resolution.
Derivative [Line Items]
Customer swap fees in non-interest income	$ 4,000	$ 1,400