Transfers of Residential Loans - Schedule of Continuing Involvement with Mortgage Loans Sold with Servicing Rights Retained (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Qualitative and Quantitative Information, Transferor's Continuing Involvement [Line Items]
Carrying Value of Assets Recorded on the Consolidated Balance Sheets	$ 532,356	$ 534,863
Unpaid Principal Balance of Sold Loans	36,116,570	46,983,388
Servicing Rights, Net [Member]
Qualitative and Quantitative Information, Transferor's Continuing Involvement [Line Items]
Carrying Value of Assets Recorded on the Consolidated Balance Sheets	510,531	509,785
Servicer And Protective Advances, Net [Member]
Qualitative and Quantitative Information, Transferor's Continuing Involvement [Line Items]
Carrying Value of Assets Recorded on the Consolidated Balance Sheets	$ 21,825	$ 25,078