Fair Value - Additional Information (Detail) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Real estate owned, net	$ 111.3	$ 104.6
Loans in process of foreclosure	209.1	418.4
Reverse Mortgage
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Real estate owned, net	98.3	90.7
Servicing
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Real estate owned, net	12.3	12.9
Other Non-Reportable Segment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Real estate owned, net	$ 0.7	1.0
Mortgage Loans Related to Non-Residual Trusts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of days delinquent	90 days
Loans 90 days or more past due, fair value	$ 0.0	1.6
Loans 90 days or more past due, unpaid principal balance	$ 31.1	$ 29.5
Mortgage Loans Held For Sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of days delinquent	90 days
Charged-Off Loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of days delinquent	90 days