Guarantor Financial Statement Information - Consolidating Statements of Cash Flow (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Operating Activities
Net income (loss) attributable to Nationstar		$ (87)	$ 58	$ (273)	$ 218
Adjustments to reconcile net income (loss) to net cash attributable to operating activities:
Deferred tax (benefit) expense				(76)	40
Net income (loss) attributable to non-controlling interests		(1)	0	(1)	0
(Gain) loss from subsidiaries				0	0
Net gain on mortgage loans held for sale		(262)	(127)	(428)	(251)
Interest income on reverse mortgage loan				(167)	(237)
Gain on sale of assets				0	(9)
Provision for servicing reserves				30	54
Fair value changes and amortization/accretion of mortgage servicing rights/liabilities				695	(155)
Fair value changes in excess spread financing				(74)	74
Fair value changes in mortgage servicing rights financing liability				11	6
Fair value changes in mortgage loan held for investment				(3)	0
Amortization of premiums, net of discount accretion				(25)	6
Depreciation and amortization for property and equipment and intangible assets		24	14	45	29
Share-based compensation				9	8
Repurchases of forward loan assets out of Ginnie Mae securitizations				(715)	(475)
Mortgage loans originated and purchased for sale, net of fees				(15,727)	(10,639)
Sales proceeds and loan payment proceeds for mortgage loans held for sale and held for investment				15,429	11,500
Changes in assets and liabilities:
Advances and other receivables				249	355
Reverse mortgage interests				1,056	1,326
Other assets				(118)	10
Payables and accrued liabilities				31	9
Net cash attributable to operating activities				(52)	1,869
Investing Activities
Acquisitions, net of cash acquired				(85)	0
Property and equipment additions, net of disposals				(27)	(31)
Purchase of forward mortgage servicing rights, net of liabilities incurred				(409)	(123)
Net proceeds from acquisition of reverse mortgage servicing portfolio and HECM related receivables					(1)
Proceeds on sale of forward and reverse mortgage servicing rights				279	0
Proceeds on sale of assets				0	13
Net cash attributable to investing activities				(242)	(142)
Financing Activities
Increase in warehouse facilities				1,173	(199)
Decrease in advance facilities				(40)	(339)
Repayment of notes payable				(294)	0
Proceeds from issuance of HECM securitizations				398	443
Proceeds from sale of HECM securitizations				20	0
Repayment of HECM securitizations				(434)	(423)
Proceeds from issuance of participating interest financing in reverse mortgage interests				156	184
Repayment of participating interest financing in reverse mortgage interests				(1,004)	(1,368)
Proceeds from the issuance of excess spread financing				437	70
Repayment of excess spread financing				(12)	(2)
Settlement of excess spread financing				(107)	(91)
Proceeds from issuance of excess spread financing					70
Repayment of nonrecourse debt – legacy assets				(6)	(6)
Repayment of finance lease liability				(2)	0
Repurchase of unsecured senior notes				0	(62)
Surrender of shares relating to stock vesting				(2)	(6)
Debt financing costs				(1)	(7)
Dividends to non-controlling interests				0	(1)
Net cash attributable to financing activities				282	(1,807)
Net decrease in cash, cash equivalents, and restricted cash				(12)	(80)
Cash, cash equivalents, and restricted cash - beginning of period				561	575
Cash, cash equivalents, and restricted cash - end of period	[1]	549	495	549	495
Eliminations
Operating Activities
Net income (loss) attributable to Nationstar		46	(76)	185	(268)
Adjustments to reconcile net income (loss) to net cash attributable to operating activities:
Deferred tax (benefit) expense				0	0
Net income (loss) attributable to non-controlling interests		0	0	0	0
(Gain) loss from subsidiaries				(185)	268
Net gain on mortgage loans held for sale		0	0	0	0
Interest income on reverse mortgage loan				0	0
Gain on sale of assets					0
Provision for servicing reserves				0	0
Fair value changes and amortization/accretion of mortgage servicing rights/liabilities				0	0
Fair value changes in excess spread financing				0	0
Fair value changes in mortgage servicing rights financing liability				0	0
Fair value changes in mortgage loan held for investment				0
Amortization of premiums, net of discount accretion				0	0
Depreciation and amortization for property and equipment and intangible assets				0	0
Share-based compensation				0	0
Repurchases of forward loan assets out of Ginnie Mae securitizations				0	0
Mortgage loans originated and purchased for sale, net of fees				0	0
Sales proceeds and loan payment proceeds for mortgage loans held for sale and held for investment				0	0
Changes in assets and liabilities:
Advances and other receivables				0	0
Reverse mortgage interests				0	0
Other assets				0	0
Payables and accrued liabilities				0	0
Net cash attributable to operating activities				0	0
Investing Activities
Acquisitions, net of cash acquired				0
Property and equipment additions, net of disposals				0	0
Purchase of forward mortgage servicing rights, net of liabilities incurred				0	0
Net proceeds from acquisition of reverse mortgage servicing portfolio and HECM related receivables					0
Proceeds on sale of forward and reverse mortgage servicing rights				0
Proceeds on sale of assets					0
Net cash attributable to investing activities				0	0
Financing Activities
Increase in warehouse facilities				0	0
Decrease in advance facilities				0	0
Repayment of notes payable				0
Proceeds from issuance of HECM securitizations				0	0
Proceeds from sale of HECM securitizations				0
Repayment of HECM securitizations				0	0
Proceeds from issuance of participating interest financing in reverse mortgage interests				0	0
Repayment of participating interest financing in reverse mortgage interests				0	0
Proceeds from the issuance of excess spread financing				0
Repayment of excess spread financing				0	0
Settlement of excess spread financing				0	0
Proceeds from issuance of excess spread financing					0
Repayment of nonrecourse debt – legacy assets				0	0
Repayment of finance lease liability				0
Repurchase of unsecured senior notes					0
Surrender of shares relating to stock vesting				0	0
Debt financing costs				0	0
Dividends to non-controlling interests					0
Net cash attributable to financing activities				0	0
Net decrease in cash, cash equivalents, and restricted cash				0	0
Cash, cash equivalents, and restricted cash - beginning of period				0	0
Cash, cash equivalents, and restricted cash - end of period		0	0	0	0
Mr. Cooper
Investing Activities
Net proceeds from acquisition of reverse mortgage servicing portfolio and HECM related receivables					0
Mr. Cooper | Reportable entities
Operating Activities
Net income (loss) attributable to Nationstar		(87)	58	(273)	218
Adjustments to reconcile net income (loss) to net cash attributable to operating activities:
Deferred tax (benefit) expense				0	0
Net income (loss) attributable to non-controlling interests		0	0	0	0
(Gain) loss from subsidiaries				196	(218)
Net gain on mortgage loans held for sale		0	0	0	0
Interest income on reverse mortgage loan				0	0
Gain on sale of assets					0
Provision for servicing reserves				0	0
Fair value changes and amortization/accretion of mortgage servicing rights/liabilities				0	0
Fair value changes in excess spread financing				0	0
Fair value changes in mortgage servicing rights financing liability				0	0
Fair value changes in mortgage loan held for investment				0
Amortization of premiums, net of discount accretion				3	0
Depreciation and amortization for property and equipment and intangible assets				0	0
Share-based compensation				0	0
Repurchases of forward loan assets out of Ginnie Mae securitizations				0	0
Mortgage loans originated and purchased for sale, net of fees				0	0
Sales proceeds and loan payment proceeds for mortgage loans held for sale and held for investment				0	0
Changes in assets and liabilities:
Advances and other receivables				0	0
Reverse mortgage interests				0	0
Other assets				0	6
Payables and accrued liabilities				74	0
Net cash attributable to operating activities				0	6
Investing Activities
Acquisitions, net of cash acquired				0
Property and equipment additions, net of disposals				0	0
Purchase of forward mortgage servicing rights, net of liabilities incurred				0	0
Proceeds on sale of forward and reverse mortgage servicing rights				0
Proceeds on sale of assets					0
Net cash attributable to investing activities				0	0
Financing Activities
Increase in warehouse facilities				0	0
Decrease in advance facilities				0	0
Repayment of notes payable				0
Proceeds from issuance of HECM securitizations				0	0
Proceeds from sale of HECM securitizations				0
Repayment of HECM securitizations				0	0
Proceeds from issuance of participating interest financing in reverse mortgage interests				0	0
Repayment of participating interest financing in reverse mortgage interests				0	0
Proceeds from the issuance of excess spread financing				0
Repayment of excess spread financing				0	0
Settlement of excess spread financing				0	0
Proceeds from issuance of excess spread financing					0
Repayment of nonrecourse debt – legacy assets				0	0
Repayment of finance lease liability				0
Repurchase of unsecured senior notes					0
Surrender of shares relating to stock vesting				0	(6)
Debt financing costs				0	0
Dividends to non-controlling interests					0
Net cash attributable to financing activities				0	(6)
Net decrease in cash, cash equivalents, and restricted cash				0	0
Cash, cash equivalents, and restricted cash - beginning of period				0	0
Cash, cash equivalents, and restricted cash - end of period		0	0	0	0
Issuer
Investing Activities
Net proceeds from acquisition of reverse mortgage servicing portfolio and HECM related receivables					(1)
Issuer | Reportable entities
Operating Activities
Net income (loss) attributable to Nationstar		(48)	58	(196)	218
Adjustments to reconcile net income (loss) to net cash attributable to operating activities:
Deferred tax (benefit) expense				(76)	41
Net income (loss) attributable to non-controlling interests		(1)	0	(1)	0
(Gain) loss from subsidiaries				(11)	(50)
Net gain on mortgage loans held for sale		(262)	(127)	(428)	(251)
Interest income on reverse mortgage loan				(167)	(237)
Gain on sale of assets					0
Provision for servicing reserves				30	54
Fair value changes and amortization/accretion of mortgage servicing rights/liabilities				690	(155)
Fair value changes in excess spread financing				(71)	73
Fair value changes in mortgage servicing rights financing liability				11	6
Fair value changes in mortgage loan held for investment				0
Amortization of premiums, net of discount accretion				(28)	9
Depreciation and amortization for property and equipment and intangible assets				37	23
Share-based compensation				7	7
Repurchases of forward loan assets out of Ginnie Mae securitizations				(715)	(475)
Mortgage loans originated and purchased for sale, net of fees				(15,727)	(10,639)
Sales proceeds and loan payment proceeds for mortgage loans held for sale and held for investment				15,420	11,490
Changes in assets and liabilities:
Advances and other receivables				249	355
Reverse mortgage interests				1,001	1,314
Other assets				(65)	(188)
Payables and accrued liabilities				(16)	13
Net cash attributable to operating activities				(56)	1,608
Investing Activities
Acquisitions, net of cash acquired				(85)
Property and equipment additions, net of disposals				(20)	(27)
Purchase of forward mortgage servicing rights, net of liabilities incurred				(409)	(117)
Proceeds on sale of forward and reverse mortgage servicing rights				279
Proceeds on sale of assets					0
Net cash attributable to investing activities				(235)	(145)
Financing Activities
Increase in warehouse facilities				1,173	(199)
Decrease in advance facilities				(13)	(57)
Repayment of notes payable				(294)
Proceeds from issuance of HECM securitizations				0	0
Proceeds from sale of HECM securitizations				0
Repayment of HECM securitizations				0	0
Proceeds from issuance of participating interest financing in reverse mortgage interests				156	184
Repayment of participating interest financing in reverse mortgage interests				(1,004)	(1,368)
Proceeds from the issuance of excess spread financing				437
Repayment of excess spread financing				(12)	(2)
Settlement of excess spread financing				(107)	(91)
Proceeds from issuance of excess spread financing					70
Repayment of nonrecourse debt – legacy assets				0	0
Repayment of finance lease liability				(2)
Repurchase of unsecured senior notes					(62)
Surrender of shares relating to stock vesting				(2)	0
Debt financing costs				(1)	(7)
Dividends to non-controlling interests					(1)
Net cash attributable to financing activities				331	(1,533)
Net decrease in cash, cash equivalents, and restricted cash				40	(70)
Cash, cash equivalents, and restricted cash - beginning of period				379	423
Cash, cash equivalents, and restricted cash - end of period		419	353	419	353
Guarantor (Subsidiaries of Issuer)
Investing Activities
Net proceeds from acquisition of reverse mortgage servicing portfolio and HECM related receivables					0
Guarantor (Subsidiaries of Issuer) | Reportable entities
Operating Activities
Net income (loss) attributable to Nationstar		3	6	7	10
Adjustments to reconcile net income (loss) to net cash attributable to operating activities:
Deferred tax (benefit) expense				0	0
Net income (loss) attributable to non-controlling interests		0	0	0	0
(Gain) loss from subsidiaries				0	0
Net gain on mortgage loans held for sale		0	0	0	0
Interest income on reverse mortgage loan				0	0
Gain on sale of assets					0
Provision for servicing reserves				0	0
Fair value changes and amortization/accretion of mortgage servicing rights/liabilities				0	0
Fair value changes in excess spread financing				0	0
Fair value changes in mortgage servicing rights financing liability				0	0
Fair value changes in mortgage loan held for investment				0
Amortization of premiums, net of discount accretion				0	0
Depreciation and amortization for property and equipment and intangible assets				0	0
Share-based compensation				0	0
Repurchases of forward loan assets out of Ginnie Mae securitizations				0	0
Mortgage loans originated and purchased for sale, net of fees				0	0
Sales proceeds and loan payment proceeds for mortgage loans held for sale and held for investment				0	0
Changes in assets and liabilities:
Advances and other receivables				0	0
Reverse mortgage interests				0	0
Other assets				(8)	(10)
Payables and accrued liabilities				1	0
Net cash attributable to operating activities				0	0
Investing Activities
Acquisitions, net of cash acquired				0
Property and equipment additions, net of disposals				0	0
Purchase of forward mortgage servicing rights, net of liabilities incurred				0	0
Proceeds on sale of forward and reverse mortgage servicing rights				0
Proceeds on sale of assets					0
Net cash attributable to investing activities				0	0
Financing Activities
Increase in warehouse facilities				0	0
Decrease in advance facilities				0	0
Repayment of notes payable				0
Proceeds from issuance of HECM securitizations				0	0
Proceeds from sale of HECM securitizations				0
Repayment of HECM securitizations				0	0
Proceeds from issuance of participating interest financing in reverse mortgage interests				0	0
Repayment of participating interest financing in reverse mortgage interests				0	0
Proceeds from the issuance of excess spread financing				0
Repayment of excess spread financing				0	0
Settlement of excess spread financing				0	0
Proceeds from issuance of excess spread financing					0
Repayment of nonrecourse debt – legacy assets				0	0
Repayment of finance lease liability				0
Repurchase of unsecured senior notes					0
Surrender of shares relating to stock vesting				0	0
Debt financing costs				0	0
Dividends to non-controlling interests					0
Net cash attributable to financing activities				0	0
Net decrease in cash, cash equivalents, and restricted cash				0	0
Cash, cash equivalents, and restricted cash - beginning of period				1	1
Cash, cash equivalents, and restricted cash - end of period		1	1	1	1
Non-Guarantor (Subsidiaries of Issuer)
Investing Activities
Net proceeds from acquisition of reverse mortgage servicing portfolio and HECM related receivables					0
Non-Guarantor (Subsidiaries of Issuer) | Reportable entities
Operating Activities
Net income (loss) attributable to Nationstar		(1)	12	4	40
Adjustments to reconcile net income (loss) to net cash attributable to operating activities:
Deferred tax (benefit) expense				0	(1)
Net income (loss) attributable to non-controlling interests		0	0	0	0
(Gain) loss from subsidiaries				0	0
Net gain on mortgage loans held for sale		0	0	0	0
Interest income on reverse mortgage loan				0	0
Gain on sale of assets					(9)
Provision for servicing reserves				0	0
Fair value changes and amortization/accretion of mortgage servicing rights/liabilities				5	0
Fair value changes in excess spread financing				(3)	1
Fair value changes in mortgage servicing rights financing liability				0	0
Fair value changes in mortgage loan held for investment				(3)
Amortization of premiums, net of discount accretion				0	(3)
Depreciation and amortization for property and equipment and intangible assets				8	6
Share-based compensation				2	1
Repurchases of forward loan assets out of Ginnie Mae securitizations				0	0
Mortgage loans originated and purchased for sale, net of fees				0	0
Sales proceeds and loan payment proceeds for mortgage loans held for sale and held for investment				9	10
Changes in assets and liabilities:
Advances and other receivables				0	0
Reverse mortgage interests				55	12
Other assets				(45)	202
Payables and accrued liabilities				(28)	(4)
Net cash attributable to operating activities				4	255
Investing Activities
Acquisitions, net of cash acquired				0
Property and equipment additions, net of disposals				(7)	(4)
Purchase of forward mortgage servicing rights, net of liabilities incurred				0	(6)
Proceeds on sale of forward and reverse mortgage servicing rights				0
Proceeds on sale of assets					13
Net cash attributable to investing activities				(7)	3
Financing Activities
Increase in warehouse facilities				0	0
Decrease in advance facilities				(27)	(282)
Repayment of notes payable				0
Proceeds from issuance of HECM securitizations				398	443
Proceeds from sale of HECM securitizations				20
Repayment of HECM securitizations				(434)	(423)
Proceeds from issuance of participating interest financing in reverse mortgage interests				0	0
Repayment of participating interest financing in reverse mortgage interests				0	0
Proceeds from the issuance of excess spread financing				0
Repayment of excess spread financing				0	0
Settlement of excess spread financing				0	0
Proceeds from issuance of excess spread financing					0
Repayment of nonrecourse debt – legacy assets				(6)	(6)
Repayment of finance lease liability				0
Repurchase of unsecured senior notes					0
Surrender of shares relating to stock vesting				0	0
Debt financing costs				0	0
Dividends to non-controlling interests					0
Net cash attributable to financing activities				(49)	(268)
Net decrease in cash, cash equivalents, and restricted cash				(52)	(10)
Cash, cash equivalents, and restricted cash - beginning of period				181	151
Cash, cash equivalents, and restricted cash - end of period		$ 129	$ 141	$ 129	$ 141

[1] The following table provides a reconciliation of cash, cash equivalents and restricted cash to amount reported within the consolidated balance sheets. Cash and cash equivalents of $245 and $185, Restricted cash of $304 and $310, and Total cash, cash equivalents, and restricted cash of $549 and $495, as of June 30, 2019 and June 30, 2018, respectively