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, 2019	Jul. 31, 2018	Sep. 30, 2019
Revenues:
Service related, net		$ 259	$ 258		$ 479
Net gain on mortgage loans held for sale		83	360		788
Total revenues		342	618		1,267
Expenses:
Salaries, wages and benefits		139	250		703
General and administrative		136	228		710
Total expenses		275	478		1,413
Other income (expenses):
Interest income		90	163		459
Interest expense		(122)	(196)		(572)
Other income (expenses)		6	0		16
Gain (loss) from subsidiaries		0	0		0
Total other income (expenses), net		(26)	(33)		(97)
Income (loss) before income tax expense (benefit)		41	107		(243)
Less: Income tax (benefit) expense		979	(24)		52
Net income (loss)		1,020	83		(191)
Less: Net loss attributable to non-controlling interests		0	(1)		(2)
Net income (loss) attributable to Successor/Predecessor		1,020	84		(189)
Eliminations
Revenues:
Service related, net		0	0		0
Net gain on mortgage loans held for sale		0	0		0
Total revenues		0	0		0
Expenses:
Salaries, wages and benefits		0	0		0
General and administrative		0	0		0
Total expenses		0	0		0
Other income (expenses):
Interest income		0	0		0
Interest expense		0	0		0
Other income (expenses)		0	0		0
Gain (loss) from subsidiaries		(57)	(192)		(7)
Total other income (expenses), net		(57)	(192)		(7)
Income (loss) before income tax expense (benefit)		(57)	(192)		(7)
Less: Income tax (benefit) expense		0	0		0
Net income (loss)		(57)	(192)		(7)
Less: Net loss attributable to non-controlling interests		0	0		0
Net income (loss) attributable to Successor/Predecessor		(57)	(192)		(7)
Mr. Cooper | Reportable entities
Revenues:
Service related, net		0	0		0
Net gain on mortgage loans held for sale		0	0		0
Total revenues		0	0		0
Expenses:
Salaries, wages and benefits		0	0		0
General and administrative		1	0		0
Total expenses		1	0		0
Other income (expenses):
Interest income		0	0		0
Interest expense		(26)	(37)		(114)
Other income (expenses)		1	0		0
Gain (loss) from subsidiaries		56	121		(75)
Total other income (expenses), net		31	84		(189)
Income (loss) before income tax expense (benefit)		30	84		(189)
Less: Income tax (benefit) expense		990	0		0
Net income (loss)		1,020	84		(189)
Less: Net loss attributable to non-controlling interests		0	0		0
Net income (loss) attributable to Successor/Predecessor		1,020	84		(189)
Issuer | Reportable entities
Revenues:
Service related, net		183	137		139
Net gain on mortgage loans held for sale		83	349		777
Total revenues		266	486		916
Expenses:
Salaries, wages and benefits		107	209		581
General and administrative		91	185		529
Total expenses		198	394		1,110
Other income (expenses):
Interest income		80	127		392
Interest expense		(87)	(143)		(411)
Other income (expenses)		5	(3)		2
Gain (loss) from subsidiaries		1	71		82
Total other income (expenses), net		(1)	52		65
Income (loss) before income tax expense (benefit)		67	144		(129)
Less: Income tax (benefit) expense		(11)	(24)		52
Net income (loss)		56	120		(77)
Less: Net loss attributable to non-controlling interests		0	(1)		(2)
Net income (loss) attributable to Successor/Predecessor		56	121		(75)
Guarantor (Subsidiaries of Issuer) | Reportable entities
Revenues:
Service related, net		4	5		16
Net gain on mortgage loans held for sale		0	0		0
Total revenues		4	5		16
Expenses:
Salaries, wages and benefits		1	1		3
General and administrative		1	0		2
Total expenses		2	1		5
Other income (expenses):
Interest income		0	0		0
Interest expense		0	0		0
Other income (expenses)		0	0		0
Gain (loss) from subsidiaries		0	0		0
Total other income (expenses), net		0	0		0
Income (loss) before income tax expense (benefit)		2	4		11
Less: Income tax (benefit) expense		0	0		0
Net income (loss)		2	4		11
Less: Net loss attributable to non-controlling interests		0	0		0
Net income (loss) attributable to Successor/Predecessor		2	4		11
Non-Guarantor (Subsidiaries of Issuer) | Reportable entities
Revenues:
Service related, net		72	116		324
Net gain on mortgage loans held for sale		0	11		11
Total revenues		72	127		335
Expenses:
Salaries, wages and benefits		31	40		119
General and administrative		43	43		179
Total expenses		74	83		298
Other income (expenses):
Interest income		10	36		67
Interest expense		(9)	(16)		(47)
Other income (expenses)		0	3		14
Gain (loss) from subsidiaries		0	0		0
Total other income (expenses), net		1	23		34
Income (loss) before income tax expense (benefit)		(1)	67		71
Less: Income tax (benefit) expense		0	0		0
Net income (loss)		(1)	67		71
Less: Net loss attributable to non-controlling interests		0	0		0
Net income (loss) attributable to Successor/Predecessor		$ (1)	$ 67		$ 71
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
Expenses:
Salaries, wages and benefits	69			426
General and administrative	173			519
Total expenses	242			945
Other income (expenses):
Interest income	48			333
Interest expense	(53)			(388)
Other income (expenses)	0			6
Gain (loss) from subsidiaries	0			0
Total other income (expenses), net	(5)			(49)
Income (loss) before income tax expense (benefit)	(83)			202
Less: Income tax (benefit) expense	19			(48)
Net income (loss)	(64)			154
Less: Net loss attributable to non-controlling interests	0			0
Net income (loss) attributable to Successor/Predecessor	(64)			154
Nationstar Mortgage Holdings Inc. | Eliminations
Revenues:
Service related, net	0			0
Net gain on mortgage loans held for sale	0			0
Total revenues	0			0
Expenses:
Salaries, wages and benefits	0			0
General and administrative	0			0
Total expenses	0			0
Other income (expenses):
Interest income	0			0
Interest expense	0			0
Other income (expenses)	0			0
Gain (loss) from subsidiaries	30			(237)
Total other income (expenses), net	30			(237)
Income (loss) before income tax expense (benefit)	30			(237)
Less: Income tax (benefit) expense	0			0
Net income (loss)	30			(237)
Less: Net loss attributable to non-controlling interests	0			0
Net income (loss) attributable to Successor/Predecessor	30			(237)
Nationstar Mortgage Holdings Inc. | Mr. Cooper | Reportable entities
Revenues:
Service related, net	0			0
Net gain on mortgage loans held for sale	0			0
Total revenues	0			0
Expenses:
Salaries, wages and benefits	0			0
General and administrative	27			27
Total expenses	27			27
Other income (expenses):
Interest income	0			0
Interest expense	0			0
Other income (expenses)	0			0
Gain (loss) from subsidiaries	(37)			181
Total other income (expenses), net	(37)			181
Income (loss) before income tax expense (benefit)	(64)			154
Less: Income tax (benefit) expense	0			0
Net income (loss)	(64)			154
Less: Net loss attributable to non-controlling interests	0			0
Net income (loss) attributable to Successor/Predecessor	(64)			154
Nationstar Mortgage Holdings Inc. | Issuer | Reportable entities
Revenues:
Service related, net	95			732
Net gain on mortgage loans held for sale	44			295
Total revenues	139			1,027
Expenses:
Salaries, wages and benefits	59			359
General and administrative	136			427
Total expenses	195			786
Other income (expenses):
Interest income	41			299
Interest expense	(49)			(364)
Other income (expenses)	0			(3)
Gain (loss) from subsidiaries	7			56
Total other income (expenses), net	(1)			(12)
Income (loss) before income tax expense (benefit)	(57)			229
Less: Income tax (benefit) expense	20			(48)
Net income (loss)	(37)			181
Less: Net loss attributable to non-controlling interests	0			0
Net income (loss) attributable to Successor/Predecessor	(37)			181
Nationstar Mortgage Holdings Inc. | Guarantor (Subsidiaries of Issuer) | Reportable entities
Revenues:
Service related, net	3			16
Net gain on mortgage loans held for sale	0			0
Total revenues	3			16
Expenses:
Salaries, wages and benefits	0			3
General and administrative	0			1
Total expenses	0			4
Other income (expenses):
Interest income	0			0
Interest expense	0			0
Other income (expenses)	0			0
Gain (loss) from subsidiaries	0			0
Total other income (expenses), net	0			0
Income (loss) before income tax expense (benefit)	3			12
Less: Income tax (benefit) expense	0			0
Net income (loss)	3			12
Less: Net loss attributable to non-controlling interests	0			0
Net income (loss) attributable to Successor/Predecessor	3			12
Nationstar Mortgage Holdings Inc. | Non-Guarantor (Subsidiaries of Issuer) | Reportable entities
Revenues:
Service related, net	22			153
Net gain on mortgage loans held for sale	0			0
Total revenues	22			153
Expenses:
Salaries, wages and benefits	10			64
General and administrative	10			64
Total expenses	20			128
Other income (expenses):
Interest income	7			34
Interest expense	(4)			(24)
Other income (expenses)	0			9
Gain (loss) from subsidiaries	0			0
Total other income (expenses), net	3			19
Income (loss) before income tax expense (benefit)	5			44
Less: Income tax (benefit) expense	(1)			0
Net income (loss)	4			44
Less: Net loss attributable to non-controlling interests	0			0
Net income (loss) attributable to Successor/Predecessor	$ 4			$ 44