Mortgage Loans Held for Sale and Investment - Reconciliation to Cash Flow (Details) - USD ($) $ in Millions	2 Months Ended	7 Months Ended	9 Months Ended
	Sep. 30, 2018	Jul. 31, 2018	Sep. 30, 2019
Loans Receivable Held-for-sale, Net, Reconciliation to Cash Flow [Roll Forward]
Balance - beginning of period	$ 1,514		$ 1,631
Mortgage loans originated and purchased, net of fees	3,459		28,199
Loans sold	(3,508)		(27,430)
Repurchase of loans out of Ginnie Mae securitizations	223		1,823
Net transfers of mortgage loans held for sale from REO in other assets and transfer from mortgage loans held for investment	4		15
Changes in fair value	(8)		19
Other purchase-related activities	(1)		10
Transfer of mortgage loans held for sale to advances/accounts receivable, net related to claims	(2)		0
Balance - end of period	1,681	$ 1,514	$ 4,267
Nationstar Mortgage Holdings Inc.
Loans Receivable Held-for-sale, Net, Reconciliation to Cash Flow [Roll Forward]
Balance - beginning of period	$ 1,514	1,891
Mortgage loans originated and purchased, net of fees		12,319
Loans sold		(13,255)
Repurchase of loans out of Ginnie Mae securitizations		544
Net transfers of mortgage loans held for sale from REO in other assets and transfer from mortgage loans held for investment		14
Changes in fair value		(1)
Other purchase-related activities		9
Transfer of mortgage loans held for sale to advances/accounts receivable, net related to claims		(7)
Balance - end of period		$ 1,514