Mortgage Servicing Rights - Prepayment fees and Other information (Detail) - MSRs - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Servicing
Expected amortization period for net carrying value	6 years 10 months 24 days
Other revenues
Servicing
Prepayment fees	$ 15.0	$ 9.3	$ 2.4

All amounts that are due to the servicer of a financial asset, excluding contractually specified servicing fees and late fees.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=56950315&loc=d3e122596-111746

Name:	us-gaap_AncillaryFeeIncomeGeneratedByServicingFinancialAssetsAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration