Netting Arrangements for Certain Financial Instruments and Securities Financing Activities - Additional Information (Detail) $ in Billions	Jun. 30, 2017 USD ($)
Derivative [Line Items]
Notional amount of derivative	$ 310.3
Exchange Cleared [Member]
Derivative [Line Items]
Notional amount of derivative	146.8
Exchange Traded [Member]
Derivative [Line Items]
Notional amount of derivative	$ 4.0

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

Name:	invest_DerivativeNotionalAmount
Namespace Prefix:	invest_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant