Transactions with Related Parties - Repurchase Agreement with PLS - Additional Information (Detail)	Dec. 19, 2016 USD ($)
VFN [Member]
Related Party Transaction [Line Items]
Maximum principal balance	$ 1,000,000,000

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

Name:	us-gaap_RelatedPartyTransactionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration