Commitments and Contingencies (Narrative) (Detail) $ in Millions	Sep. 30, 2018 USD ($) Lawsuits
Commitments and Contingencies [Abstract]
Other material lawsuits pending \| Lawsuits	0
Operating leases future minimum payments due \| $	$ 34
Pledged Sales Tax Base Amount [Member]
Loss Contingencies [Line Items]
COFINA and PR Commonwealth settlement percentage	53.65%
Cash Held In Trust BONY Mellon [Member]
Loss Contingencies [Line Items]
COFINA and PR Commonwealth settlement percentage	100.00%

Amount of required minimum rental payments for leases having an initial or remaining non-cancelable letter-terms in excess of one year.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 10
-Section 55
-Paragraph 40
-Subparagraph (Note 3)
-URI http://asc.fasb.org/extlink&oid=82846649&loc=d3e38371-112697

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 20
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=77902758&loc=d3e41502-112717

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