Business Segment Reporting - Financial Information (Details) $ in Millions	1 Months Ended	2 Months Ended	3 Months Ended	7 Months Ended	9 Months Ended
	Jul. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($)	Jul. 31, 2018 USD ($)	Sep. 30, 2019 USD ($) segment	Dec. 31, 2018 USD ($)
Segment Reporting [Abstract]
Number of reportable segments | segment					4
Revenues:
Service related, net		$ 259	$ 258		$ 479
Net gain on mortgage loans held for sale		83	360		788
Total revenues		342	618		1,267
Total Expenses		275	478		1,413
Other income (expenses)
Interest income		90	163		459
Interest expense		(122)	(196)		(572)
Other		6	0		16
Total other income (expenses), net		(26)	(33)		(97)
Income (loss) before income tax expense (benefit)		41	107		(243)
Depreciation and amortization for property and equipment and intangible assets		15	22		67
Total assets		17,728	18,478		18,478	$ 16,973
Servicing Segment
Revenues:
Net gain on mortgage loans held for sale					90
Operating Segments
Revenues:
Service related, net		259	258		479
Net gain on mortgage loans held for sale		83	349		777
Total revenues		342	607		1,256
Total Expenses		241	425		1,258
Other income (expenses)
Interest income		88	161		452
Interest expense		(85)	(144)		(410)
Other		6	2		18
Total other income (expenses), net		9	19		60
Income (loss) before income tax expense (benefit)		110	201		58
Depreciation and amortization for property and equipment and intangible assets		8	13		37
Total assets		15,983	16,364		16,364
Operating Segments | Servicing Segment
Revenues:
Service related, net		183	163		198
Net gain on mortgage loans held for sale		0	0		0
Total revenues		183	163		198
Total Expenses		104	171		555
Other income (expenses)
Interest income		78	137		388
Interest expense		(74)	(120)		(343)
Other		5	0		0
Total other income (expenses), net		9	17		45
Income (loss) before income tax expense (benefit)		88	9		(312)
Depreciation and amortization for property and equipment and intangible assets		4	5		13
Total assets		14,166	12,049		12,049
Operating Segments | Originations Segment
Revenues:
Service related, net		10	22		57
Net gain on mortgage loans held for sale		76	312		687
Total revenues		86	334		744
Total Expenses		66	155		404
Other income (expenses)
Interest income		10	24		64
Interest expense		(10)	(24)		(67)
Other		1	(1)		4
Total other income (expenses), net		1	(1)		1
Income (loss) before income tax expense (benefit)		21	178		341
Depreciation and amortization for property and equipment and intangible assets		2	4		13
Total assets		4,892	8,450		8,450
Operating Segments | Xome Segment
Revenues:
Service related, net		73	112		316
Net gain on mortgage loans held for sale		0	0		0
Total revenues		73	112		316
Total Expenses		71	101		301
Other income (expenses)
Interest income		0	0		0
Interest expense		(1)	0		0
Other		0	3		14
Total other income (expenses), net		(1)	3		14
Income (loss) before income tax expense (benefit)		1	14		29
Depreciation and amortization for property and equipment and intangible assets		2	4		11
Total assets		457	515		515
Eliminations/Reclassification
Revenues:
Service related, net		(7)	(39)		(92)
Net gain on mortgage loans held for sale		7	37		90
Total revenues		0	(2)		(2)
Total Expenses		0	(2)		(2)
Other income (expenses)
Interest income		0	0		0
Interest expense		0	0		0
Other		0	0		0
Total other income (expenses), net		0	0		0
Income (loss) before income tax expense (benefit)		0	0		0
Depreciation and amortization for property and equipment and intangible assets		0	0		0
Total assets		(3,532)	(4,650)		(4,650)
Corporate/Other
Revenues:
Service related, net		0	0		0
Net gain on mortgage loans held for sale		0	11		11
Total revenues		0	11		11
Total Expenses		34	53		155
Other income (expenses)
Interest income		2	2		7
Interest expense		(37)	(52)		(162)
Other		0	(2)		(2)
Total other income (expenses), net		(35)	(52)		(157)
Income (loss) before income tax expense (benefit)		(69)	(94)		(301)
Depreciation and amortization for property and equipment and intangible assets		7	9		30
Total assets		$ 1,745	$ 2,114		$ 2,114
Nationstar Mortgage Holdings Inc.
Revenues:
Service related, net	$ 120			$ 901
Net gain on mortgage loans held for sale	44			295
Total revenues	164			1,196
Total Expenses	242			945
Other income (expenses)
Interest income	48			333
Interest expense	(53)			(388)
Other	0			6
Total other income (expenses), net	(5)			(49)
Income (loss) before income tax expense (benefit)	(83)			202
Depreciation and amortization for property and equipment and intangible assets	4			33
Total assets	17,026			17,026
Nationstar Mortgage Holdings Inc. | Operating Segments
Revenues:
Service related, net	120			900
Net gain on mortgage loans held for sale	44			295
Total revenues	164			1,195
Total Expenses	179			842
Other income (expenses)
Interest income	47			326
Interest expense	(41)			(305)
Other	0			8
Total other income (expenses), net	6			29
Income (loss) before income tax expense (benefit)	(9)			382
Depreciation and amortization for property and equipment and intangible assets	4			29
Total assets	16,113			16,113
Nationstar Mortgage Holdings Inc. | Operating Segments | Servicing Segment
Revenues:
Service related, net	97			740
Net gain on mortgage loans held for sale	0			0
Total revenues	97			740
Total Expenses	126			474
Other income (expenses)
Interest income	41			288
Interest expense	(35)			(268)
Other	0			(1)
Total other income (expenses), net	6			19
Income (loss) before income tax expense (benefit)	(23)			285
Depreciation and amortization for property and equipment and intangible assets	2			15
Total assets	14,578			14,578
Nationstar Mortgage Holdings Inc. | Operating Segments | Originations Segment
Revenues:
Service related, net	4			36
Net gain on mortgage loans held for sale	41			270
Total revenues	45			306
Total Expenses	34			245
Other income (expenses)
Interest income	6			38
Interest expense	(6)			(37)
Other	0			0
Total other income (expenses), net	0			1
Income (loss) before income tax expense (benefit)	11			62
Depreciation and amortization for property and equipment and intangible assets	1			7
Total assets	4,701			4,701
Nationstar Mortgage Holdings Inc. | Operating Segments | Xome Segment
Revenues:
Service related, net	22			149
Net gain on mortgage loans held for sale	0			0
Total revenues	22			149
Total Expenses	19			123
Other income (expenses)
Interest income	0			0
Interest expense	0			0
Other	0			9
Total other income (expenses), net	0			9
Income (loss) before income tax expense (benefit)	3			35
Depreciation and amortization for property and equipment and intangible assets	1			7
Total assets	425			425
Nationstar Mortgage Holdings Inc. | Eliminations/Reclassification
Revenues:
Service related, net	(3)			(25)
Net gain on mortgage loans held for sale	3			25
Total revenues	0			0
Total Expenses	0			0
Other income (expenses)
Interest income	0			0
Interest expense	0			0
Other	0			0
Total other income (expenses), net	0			0
Income (loss) before income tax expense (benefit)	0			0
Depreciation and amortization for property and equipment and intangible assets	0			0
Total assets	(3,591)			(3,591)
Nationstar Mortgage Holdings Inc. | Corporate/Other
Revenues:
Service related, net	0			1
Net gain on mortgage loans held for sale	0			0
Total revenues	0			1
Total Expenses	63			103
Other income (expenses)
Interest income	1			7
Interest expense	(12)			(83)
Other	0			(2)
Total other income (expenses), net	(11)			(78)
Income (loss) before income tax expense (benefit)	(74)			(180)
Depreciation and amortization for property and equipment and intangible assets	0			4
Total assets	$ 913			$ 913