Servicing of Residential Loans - Schedule of Total Servicing Portfolio (Detail) $ in Thousands	Dec. 31, 2018 USD ($) Account	Dec. 31, 2017 USD ($) Account
Servicing Portfolio [Line Items]
Number of Accounts | Account	1,479,167	1,678,493
Unpaid Principal Balance | $	$ 187,238,536	$ 207,864,813
Third-Party Credit Owners [Member]
Servicing Portfolio [Line Items]
Number of Accounts | Account	1,422,849	1,596,013
Unpaid Principal Balance | $	$ 177,761,736	$ 196,341,996
Third-Party Credit Owners [Member] | Capitalized Servicing Rights [Member]
Servicing Portfolio [Line Items]
Number of Accounts | Account	648,272	854,292
Unpaid Principal Balance | $	$ 66,032,203	$ 93,599,077
Third-Party Credit Owners [Member] | Capitalized Subservicing [Member]
Servicing Portfolio [Line Items]
Number of Accounts | Account	21,650	29,681
Unpaid Principal Balance | $	$ 2,317,501	$ 3,242,241
Third-Party Credit Owners [Member] | Subservicing [Member]
Servicing Portfolio [Line Items]
Number of Accounts | Account	752,927	712,040
Unpaid Principal Balance | $	$ 109,412,032	$ 99,500,678
On-balance Sheet Residential Loans and Real Estate Owned [Member]
Servicing Portfolio [Line Items]
Number of Accounts | Account	56,318	82,480
Unpaid Principal Balance | $	$ 9,476,800	$ 11,522,817