Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Convertible and Long-term Debt Obligations - Warehouse Agreement Facility - Additional Information (Detail) - Warehouse Agreements [Member] - Non-recourse debt [Member] - USD ($)	Oct. 18, 2017	Sep. 30, 2017
Debt Instrument [Line Items]
Maximum amount to be borrowed		$ 600,000,000
Subsequent Event
Debt Instrument [Line Items]
Maximum amount to be borrowed	$ 1,100,000,000