Nature of Business and Basis of Presentation	12 Months Ended
Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Business and Basis of Presentation	1. Nature of Business and Basis of Presentation Nature of Business Mr. Cooper Group Inc. collectively with its consolidated subsidiaries, (“Mr. Cooper”, the “Company”, “we”, “us” or “our”) provides servicing, origination and transaction-based services related to single family residences throughout the United States with operations under its primary brands: Mr. Cooper® and Xome®. Mr. Cooper is one of the largest home loan servicers in the country focused on delivering a variety of servicing and lending products, services and technologies. Xome provides technology and data enhanced solutions to homebuyers, home sellers, real estate agents and mortgage companies. The Company’s corporate website is located at www.mrcoopergroup.com. Mr. Cooper, which was previously known as WMIH Corp. (“WMIH”), is a corporation duly organized and existing under the laws of the State of Delaware since May 11, 2015. On July 31, 2018, Wand Merger Corporation, a wholly owned subsidiary of WMIH merged with and into Nationstar Mortgage Holdings Inc. (“Nationstar”), with Nationstar continuing as a wholly owned subsidiary of WMIH (the “Merger”). Prior to the Merger, WMIH had limited operations other than its reinsurance business that operated in runoff mode and focused on identifying and consummating an accretive acquisition transaction across a broad array of industries, with a primary focus on the financial institutions sector. As a result of the Merger, shares of Nationstar common stock were delisted from the New York Stock Exchange. Following the Merger closing, the combined company traded on NASDAQ under the ticker symbol “WMIH” until October 10, 2018, when WMIH changed its name to “Mr. Cooper Group Inc.” and its ticker symbol to “COOP”. Basis of Presentation For the purpose of financial statement presentation, Mr. Cooper was determined to be the accounting acquirer in the Merger, and Nationstar’s assets and liabilities were recorded at estimated fair value as of the acquisition date. Mr. Cooper’s interim consolidated financial statements for periods following the Merger closing are labeled “Successor” and reflect the acquired assets and assumed liabilities from Nationstar. Under Securities and Exchange Commission (“SEC”) rules, when a registrant succeeds to substantially all of the business of another entity and the registrant’s own operations before the succession appear insignificant relative to the operations assumed or acquired, the registrant is required to present financial information for the acquired entity (the “Predecessor”) for all comparable periods being presented before the acquisition. Due to the acquisition, the Predecessor and Successor financial statements have been prepared on different basis of accounting and are therefore not comparable. Pursuant to the Merger, Nationstar is considered the predecessor company. Therefore, the Company is providing additional information in the accompanying consolidated financial statements regarding Nationstar’s business for periods prior to July 31, 2018. The predecessor’s company financial information is labeled “Predecessor” in these consolidated financial statements. The consolidated financial statements of the Company and Predecessor have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”). The significant accounting policies described below, together with the other notes that follow, are an integral part of the consolidated financial statements. Basis of Consolidation The basis of consolidation described below was adopted by Nationstar and applied to the Predecessor financial statements for the periods impacted by the adoption. The Successor’s financial statements reflect the adoption of such standards. The consolidated financial statements include the accounts of the Company, its wholly owned subsidiaries, other entities in which the Company has a controlling financial interest, and those variable interest entities (“VIE”) where the Company’s wholly owned subsidiaries are the primary beneficiaries. Assets and liabilities of VIEs and their respective results of operations are consolidated from the date that the Company became the primary beneficiary through the date the Company ceases to be the primary beneficiary. The Company applies the equity method of accounting to investments where it is able to exercise significant influence, but not control, over the policies and procedures of the entity and owns less than 50% of the voting interests. Investments in certain companies over which the Company does not exert significant influence are accounted for as cost method investments. Intercompany balances and transactions on consolidated entities have been eliminated. Use of Estimates The preparation of the consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Actual results could differ from these estimates due to factors such as adverse changes in the economy, increases in interest rates, secondary market pricing for loans held for sale and derivatives, strength of underwriting and servicing practices, changes in prepayment assumptions, declines in home prices or discrete events adversely affecting specific borrowers, and such differences could be material. Recent Accounting Guidance Adopted Accounting Standards Update No. 2016-02, Leases (Topic 842) (“ASU 2016-02”), No. 2018-10, Codification Improvements to Topic 842, Leases (“ASU 2018-10”), and No. 2018-11, Leases (Topic 842): Targeted Improvements (“ASU 2018-11”), primarily impact lessee accounting by requiring the recognition of a right-of-use asset and a corresponding lease liability on the balance sheet for long-term lease agreements. ASU 2016-02 was effective for the Company on January 1, 2019. ASU 2016-02 provides for a modified retrospective transition approach requiring lessees to recognize and measure leases on the balance sheet at the beginning of either the earliest period presented or as of the beginning of the period of adoption with the option to elect certain practical expedients. The Company has elected to apply ASU 2016-02 as of the beginning of the period of adoption (January 1, 2019) and has not restated comparative periods. The Company elected the package of practical expedients, which, among other items, permits the Company not to reassess under the new standard its prior conclusions about lease identification, lease classification and initial direct costs. The Company also elected the short-term lease recognition exemption for all leases that qualify. Under this practical expedient, for those leases that qualify, the Company does not recognize right-of-use (“ROU”) assets or lease liabilities, which includes not recognizing ROU assets or lease liabilities for existing short-term leases of those assets in transition. The Company also elected the practical expedient to not separate lease and non-lease components for all of our leases. The Company did not elect the use-of-hindsight practical expedient. As a result of implementing ASU 2016-02, the Company recognized an operating lease ROU asset of $114 and an operating lease liability of $124 on January 1, 2019, with no impact on its consolidated statement of operations. The ROU asset and operating lease liability are recorded in other assets, and payables and other liabilities, respectively, in the consolidated balance sheets. See Note 9, Leases, for additional information. Accounting Standards Update No. 2018-15, Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40 - Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract" (“ASU 2018-15”) aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software (and hosting arrangements that include an internal-use software license). ASU 2018-15 was effective for the Company on January 1, 2020. Early adoption is permitted, including adoption in any interim period. In the first quarter of 2019, the Company early adopted ASU 2018-15. The standard did not have a material impact to the Company’s consolidated financial statements.

1. Nature of Business and Basis of Presentation

Nature of Business

Mr. Cooper Group Inc. collectively with its consolidated subsidiaries, (“Mr. Cooper”, the “Company”, “we”, “us” or “our”) provides servicing, origination and transaction-based services related to single family residences throughout the United States with operations under its primary brands: Mr. Cooper® and Xome®. Mr. Cooper is one of the largest home loan servicers in the country focused on delivering a variety of servicing and lending products, services and technologies. Xome provides technology and data enhanced solutions to homebuyers, home sellers, real estate agents and mortgage companies. The Company’s corporate website is located at www.mrcoopergroup.com.

Mr. Cooper, which was previously known as WMIH Corp. (“WMIH”), is a corporation duly organized and existing under the laws of the State of Delaware since May 11, 2015. On July 31, 2018, Wand Merger Corporation, a wholly owned subsidiary of WMIH merged with and into Nationstar Mortgage Holdings Inc. (“Nationstar”), with Nationstar continuing as a wholly owned subsidiary of WMIH (the “Merger”). Prior to the Merger, WMIH had limited operations other than its reinsurance business that operated in runoff mode and focused on identifying and consummating an accretive acquisition transaction across a broad array of industries, with a primary focus on the financial institutions sector. As a result of the Merger, shares of Nationstar common stock were delisted from the New York Stock Exchange. Following the Merger closing, the combined company traded on NASDAQ under the ticker symbol “WMIH” until October 10, 2018, when WMIH changed its name to “Mr. Cooper Group Inc.” and its ticker symbol to “COOP”.

Basis of Presentation

For the purpose of financial statement presentation, Mr. Cooper was determined to be the accounting acquirer in the Merger, and Nationstar’s assets and liabilities were recorded at estimated fair value as of the acquisition date. Mr. Cooper’s interim consolidated financial statements for periods following the Merger closing are labeled “Successor” and reflect the acquired assets and assumed liabilities from Nationstar.

Under Securities and Exchange Commission (“SEC”) rules, when a registrant succeeds to substantially all of the business of another entity and the registrant’s own operations before the succession appear insignificant relative to the operations assumed or acquired, the registrant is required to present financial information for the acquired entity (the “Predecessor”) for all comparable periods being presented before the acquisition. Due to the acquisition, the Predecessor and Successor financial statements have been prepared on different basis of accounting and are therefore not comparable.

Pursuant to the Merger, Nationstar is considered the predecessor company. Therefore, the Company is providing additional information in the accompanying consolidated financial statements regarding Nationstar’s business for periods prior to July 31, 2018. The predecessor’s company financial information is labeled “Predecessor” in these consolidated financial statements.

The consolidated financial statements of the Company and Predecessor have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”). The significant accounting policies described below, together with the other notes that follow, are an integral part of the consolidated financial statements.

Basis of Consolidation

The basis of consolidation described below was adopted by Nationstar and applied to the Predecessor financial statements for the periods impacted by the adoption. The Successor’s financial statements reflect the adoption of such standards.

The consolidated financial statements include the accounts of the Company, its wholly owned subsidiaries, other entities in which the Company has a controlling financial interest, and those variable interest entities (“VIE”) where the Company’s wholly owned subsidiaries are the primary beneficiaries. Assets and liabilities of VIEs and their respective results of operations are consolidated from the date that the Company became the primary beneficiary through the date the Company ceases to be the primary beneficiary. The Company applies the equity method of accounting to investments where it is able to exercise significant influence, but not control, over the policies and procedures of the entity and owns less than 50% of the voting interests. Investments in certain companies over which the Company does not exert significant influence are accounted for as cost method investments. Intercompany balances and transactions on consolidated entities have been eliminated.

Use of Estimates

The preparation of the consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Actual results could differ from these estimates due to factors such as adverse changes in the economy, increases in interest rates, secondary market pricing for loans held for sale and derivatives, strength of underwriting and servicing practices, changes in prepayment assumptions, declines in home prices or discrete events adversely affecting specific borrowers, and such differences could be material.

Recent Accounting Guidance Adopted

Accounting Standards Update No. 2016-02, Leases (Topic 842) (“ASU 2016-02”), No. 2018-10, Codification Improvements to Topic 842, Leases (“ASU 2018-10”), and No. 2018-11, Leases (Topic 842): Targeted Improvements (“ASU 2018-11”), primarily impact lessee accounting by requiring the recognition of a right-of-use asset and a corresponding lease liability on the balance sheet for long-term lease agreements. ASU 2016-02 was effective for the Company on January 1, 2019. ASU 2016-02 provides for a modified retrospective transition approach requiring lessees to recognize and measure leases on the balance sheet at the beginning of either the earliest period presented or as of the beginning of the period of adoption with the option to elect certain practical expedients. The Company has elected to apply ASU 2016-02 as of the beginning of the period of adoption (January 1, 2019) and has not restated comparative periods. The Company elected the package of practical expedients, which, among other items, permits the Company not to reassess under the new standard its prior conclusions about lease identification, lease classification and initial direct costs. The Company also elected the short-term lease recognition exemption for all leases that qualify. Under this practical expedient, for those leases that qualify, the Company does not recognize right-of-use (“ROU”) assets or lease liabilities, which includes not recognizing ROU assets or lease liabilities for existing short-term leases of those assets in transition. The Company also elected the practical expedient to not separate lease and non-lease components for all of our leases. The Company did not elect the use-of-hindsight practical expedient. As a result of implementing ASU 2016-02, the Company recognized an operating lease ROU asset of $114 and an operating lease liability of $124 on January 1, 2019, with no impact on its consolidated statement of operations. The ROU asset and operating lease liability are recorded in other assets, and payables and other liabilities, respectively, in the consolidated balance sheets. See Note 9, Leases, for additional information.

Accounting Standards Update No. 2018-15, Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40 - Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract" (“ASU 2018-15”) aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software (and hosting arrangements that include an internal-use software license). ASU 2018-15 was effective for the Company on January 1, 2020. Early adoption is permitted, including adoption in any interim period. In the first quarter of 2019, the Company early adopted ASU 2018-15. The standard did not have a material impact to the Company’s consolidated financial statements.