Servicing of Residential Loans - Additional Information (Detail) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Mortgage Loan
Servicing Asset at Amortized Cost [Line Items]
Fair value of servicing rights	$ 62.0	$ 79.9
Reverse Loan
Servicing Asset at Amortized Cost [Line Items]
Fair value of servicing rights	$ 5.7	$ 7.3

Fair value of contract to service financial assets under which the benefits of servicing are expected to more than adequately compensate the servicer.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 4
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=68078379&loc=d3e122739-111746

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=7516967&loc=d3e66267-113978

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