Guarantor Financial Statement Information - Consolidating Statements of Operations (Details) - USD ($) $ in Millions	1 Months Ended	2 Months Ended	3 Months Ended	7 Months Ended	9 Months Ended
	Jul. 31, 2018	Sep. 30, 2018	Sep. 30, 2017	Jul. 31, 2018	Sep. 30, 2017
Revenues:
Service related, net		$ 259
Net gain on mortgage loans held for sale		83
Total revenues		342
Expenses:
Salaries, wages and benefits		139
General and administrative		136
Total expenses		275
Other income (expenses):
Interest income		90
Interest expense		(122)
Other income (expenses)		6
Gain (loss) from subsidiaries		0
Total other income (expenses), net		(26)
Income before income tax expense (benefit)		41
Less: Income tax expense (benefit)		(979)
Net income (loss)		1,020
Less: Net income attributable to non-controlling interests		0
Net income (loss) attributable to Successor/Predecessor		1,020
Predecessor
Revenues:
Service related, net	$ 120		$ 252	$ 901	$ 748
Net gain on mortgage loans held for sale	44		154	295	465
Total revenues	164		406	1,196	1,213
Expenses:
Salaries, wages and benefits	69		183	426	557
General and administrative	173		185	519	547
Total expenses	242		368	945	1,104
Other income (expenses):
Interest income	48		159	333	437
Interest expense	(53)		(183)	(388)	(564)
Other income (expenses)	0		(2)	6	4
Gain (loss) from subsidiaries	0		0	0	0
Total other income (expenses), net	(5)		(26)	(49)	(123)
Income before income tax expense (benefit)	(83)		12	202	(14)
Less: Income tax expense (benefit)	(19)		5	48	(4)
Net income (loss)	(64)		7	154	(10)
Less: Net income attributable to non-controlling interests	0		0	0	1
Net income (loss) attributable to Successor/Predecessor	(64)		7	154	(11)
Eliminations
Revenues:
Service related, net		0
Net gain on mortgage loans held for sale		0
Total revenues		0
Expenses:
Salaries, wages and benefits		0
General and administrative		0
Total expenses		0
Other income (expenses):
Interest income		0
Interest expense		0
Other income (expenses)		0
Gain (loss) from subsidiaries		(57)
Total other income (expenses), net		(57)
Income before income tax expense (benefit)		(57)
Less: Income tax expense (benefit)		0
Net income (loss)		(57)
Less: Net income attributable to non-controlling interests		0
Net income (loss) attributable to Successor/Predecessor		(57)
Eliminations | Predecessor
Revenues:
Service related, net	0		0	0	0
Net gain on mortgage loans held for sale	0		0	0	0
Total revenues	0		0	0	0
Expenses:
Salaries, wages and benefits	0		0	0	0
General and administrative	0		0	0	0
Total expenses	0		0	0	0
Other income (expenses):
Interest income	0		0	0	0
Interest expense	0		0	0	0
Other income (expenses)	0		0	0	0
Gain (loss) from subsidiaries	30		(18)	(237)	(29)
Total other income (expenses), net	30		(18)	(237)	(29)
Income before income tax expense (benefit)	30		(18)	(237)	(29)
Less: Income tax expense (benefit)	0		0	0	0
Net income (loss)	30		(18)	(237)	(29)
Less: Net income attributable to non-controlling interests	0		0	0	0
Net income (loss) attributable to Successor/Predecessor	30		(18)	(237)	(29)
Mr. Cooper | Reportable entities
Revenues:
Service related, net		0
Net gain on mortgage loans held for sale		0
Total revenues		0
Expenses:
Salaries, wages and benefits		0
General and administrative		1
Total expenses		1
Other income (expenses):
Interest income		0
Interest expense		(26)
Other income (expenses)		1
Gain (loss) from subsidiaries		56
Total other income (expenses), net		31
Income before income tax expense (benefit)		30
Less: Income tax expense (benefit)		(990)
Net income (loss)		1,020
Less: Net income attributable to non-controlling interests		0
Net income (loss) attributable to Successor/Predecessor		1,020
Mr. Cooper | Reportable entities | Predecessor
Revenues:
Service related, net	0		0	0	0
Net gain on mortgage loans held for sale	0		0	0	0
Total revenues	0		0	0	0
Expenses:
Salaries, wages and benefits	0		0	0	0
General and administrative	27		0	27	0
Total expenses	27		0	27	0
Other income (expenses):
Interest income	0		0	0	0
Interest expense	0		0	0	0
Other income (expenses)	0		0	0	0
Gain (loss) from subsidiaries	(37)		7	181	(11)
Total other income (expenses), net	(37)		7	181	(11)
Income before income tax expense (benefit)	(64)		7	154	(11)
Less: Income tax expense (benefit)	0		0	0	0
Net income (loss)	(64)		7	154	(11)
Less: Net income attributable to non-controlling interests	0		0	0	0
Net income (loss) attributable to Successor/Predecessor	(64)		7	154	(11)
Issuer | Reportable entities
Revenues:
Service related, net		183
Net gain on mortgage loans held for sale		83
Total revenues		266
Expenses:
Salaries, wages and benefits		107
General and administrative		91
Total expenses		198
Other income (expenses):
Interest income		80
Interest expense		(87)
Other income (expenses)		5
Gain (loss) from subsidiaries		1
Total other income (expenses), net		(1)
Income before income tax expense (benefit)		67
Less: Income tax expense (benefit)		11
Net income (loss)		56
Less: Net income attributable to non-controlling interests		0
Net income (loss) attributable to Successor/Predecessor		56
Issuer | Reportable entities | Predecessor
Revenues:
Service related, net	95		181	732	497
Net gain on mortgage loans held for sale	44		153	295	464
Total revenues	139		334	1,027	961
Expenses:
Salaries, wages and benefits	59		153	359	451
General and administrative	136		154	427	435
Total expenses	195		307	786	886
Other income (expenses):
Interest income	41		147	299	398
Interest expense	(49)		(170)	(364)	(522)
Other income (expenses)	0		(3)	(3)	(5)
Gain (loss) from subsidiaries	7		11	56	40
Total other income (expenses), net	(1)		(15)	(12)	(89)
Income before income tax expense (benefit)	(57)		12	229	(14)
Less: Income tax expense (benefit)	(20)		5	48	(4)
Net income (loss)	(37)		7	181	(10)
Less: Net income attributable to non-controlling interests	0		0	0	1
Net income (loss) attributable to Successor/Predecessor	(37)		7	181	(11)
Guarantor (Subsidiaries of Issuer) | Reportable entities
Revenues:
Service related, net		4
Net gain on mortgage loans held for sale		0
Total revenues		4
Expenses:
Salaries, wages and benefits		1
General and administrative		1
Total expenses		2
Other income (expenses):
Interest income		0
Interest expense		0
Other income (expenses)		0
Gain (loss) from subsidiaries		0
Total other income (expenses), net		0
Income before income tax expense (benefit)		2
Less: Income tax expense (benefit)		0
Net income (loss)		2
Less: Net income attributable to non-controlling interests		0
Net income (loss) attributable to Successor/Predecessor		2
Guarantor (Subsidiaries of Issuer) | Reportable entities | Predecessor
Revenues:
Service related, net	3		7	16	21
Net gain on mortgage loans held for sale	0		0	0	0
Total revenues	3		7	16	21
Expenses:
Salaries, wages and benefits	0		1	3	3
General and administrative	0		4	1	10
Total expenses	0		5	4	13
Other income (expenses):
Interest income	0		0	0	0
Interest expense	0		0	0	0
Other income (expenses)	0		0	0	0
Gain (loss) from subsidiaries	0		0	0	0
Total other income (expenses), net	0		0	0	0
Income before income tax expense (benefit)	3		2	12	8
Less: Income tax expense (benefit)	0		0	0	0
Net income (loss)	3		2	12	8
Less: Net income attributable to non-controlling interests	0		0	0	0
Net income (loss) attributable to Successor/Predecessor	3		2	12	8
Non-Guarantor (Subsidiaries of Issuer) | Reportable entities
Revenues:
Service related, net		72
Net gain on mortgage loans held for sale		0
Total revenues		72
Expenses:
Salaries, wages and benefits		31
General and administrative		43
Total expenses		74
Other income (expenses):
Interest income		10
Interest expense		(9)
Other income (expenses)		0
Gain (loss) from subsidiaries		0
Total other income (expenses), net		1
Income before income tax expense (benefit)		(1)
Less: Income tax expense (benefit)		0
Net income (loss)		(1)
Less: Net income attributable to non-controlling interests		0
Net income (loss) attributable to Successor/Predecessor		$ (1)
Non-Guarantor (Subsidiaries of Issuer) | Reportable entities | Predecessor
Revenues:
Service related, net	22		64	153	230
Net gain on mortgage loans held for sale	0		1	0	1
Total revenues	22		65	153	231
Expenses:
Salaries, wages and benefits	10		29	64	103
General and administrative	10		27	64	102
Total expenses	20		56	128	205
Other income (expenses):
Interest income	7		12	34	39
Interest expense	(4)		(13)	(24)	(42)
Other income (expenses)	0		1	9	9
Gain (loss) from subsidiaries	0		0	0	0
Total other income (expenses), net	3		0	19	6
Income before income tax expense (benefit)	5		9	44	32
Less: Income tax expense (benefit)	1		0	0	0
Net income (loss)	4		9	44	32
Less: Net income attributable to non-controlling interests	0		0	0	0
Net income (loss) attributable to Successor/Predecessor	$ 4		$ 9	$ 44	$ 32