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Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275

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- Definition

Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

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Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during the fourth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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- References

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13854-109267

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13777-109266

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
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-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

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Amount of insurance premium revenue recognized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1(e))
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

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- Definition

The amount of impairment loss recognized in the period resulting from the write-down of the carrying amount of a finite-lived intangible asset to fair value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16373-109275

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Goodwill and Intangible Assets, Net - Additional Information (Details)	3 Months Ended			12 Months Ended
	Dec. 31, 2017 USD ($) medical_member	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Dec. 31, 2017 USD ($) medical_member	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Finite-Lived Intangible Assets [Line Items]
Premium revenue				$ 18,854,000,000	$ 16,445,000,000	$ 13,261,000,000
Goodwill impairment charges				434,000,000	0
Future Amortization Expenses
Future amortization expense, 2018	$ 21,000,000			21,000,000
Future amortization expense, 2019	18,000,000			18,000,000
Future amortization expense, 2020	14,000,000			14,000,000
Future amortization expense, 2021	5,000,000			5,000,000
Future amortization expense, 2022	3,000,000			3,000,000
Health Plans
Finite-Lived Intangible Assets [Line Items]
Premium revenue				18,854,000,000	16,445,000,000	13,261,000,000
Goodwill impairment charges				244,000,000
Molina Medicaid Solutions
Finite-Lived Intangible Assets [Line Items]
Goodwill impairment charges				28,000,000
Other
Finite-Lived Intangible Assets [Line Items]
Goodwill impairment charges				$ 162,000,000
Impairment of intangible assets			$ 11,000,000
Minimum
Finite-Lived Intangible Assets [Line Items]
Weighted average amortization period				5 years
Maximum
Finite-Lived Intangible Assets [Line Items]
Weighted average amortization period				15 years
Subsidiaries \| Molina Medicaid Solutions
Finite-Lived Intangible Assets [Line Items]
Goodwill impairment charges		$ 28,000,000
PCC \| Subsidiaries
Finite-Lived Intangible Assets [Line Items]
Goodwill impairment charges		$ 101,000,000	59,000,000
Other Subsidiary \| Subsidiaries
Finite-Lived Intangible Assets [Line Items]
Goodwill impairment charges			$ 2,000,000
Florida \| Health Plans
Finite-Lived Intangible Assets [Line Items]
Premium revenue				$ 2,568,000,000	1,938,000,000	1,199,000,000
Florida \| Contract rights and licenses \| Health Plans
Finite-Lived Intangible Assets [Line Items]
Impairment of intangible assets	$ 15,000,000
Miami Dade and Monroe Counties \| Health Plans
Finite-Lived Intangible Assets [Line Items]
Number of members served, approximately (in member) \| medical_member	59,000			59,000
New Mexico \| Health Plans
Finite-Lived Intangible Assets [Line Items]
Premium revenue				$ 1,368,000,000	1,305,000,000	1,237,000,000
New Mexico \| Contract rights and licenses \| Health Plans
Finite-Lived Intangible Assets [Line Items]
Impairment of intangible assets	$ 10,000,000
Illinois \| Health Plans
Finite-Lived Intangible Assets [Line Items]
Premium revenue				593,000,000	603,000,000	398,000,000
Goodwill impairment charges	45,000,000
New York \| Health Plans
Finite-Lived Intangible Assets [Line Items]
Premium revenue				$ 181,000,000	$ 82,000,000	$ 0
Goodwill impairment charges	$ 1,000,000
Medicaid \| Florida \| Health Plans
Finite-Lived Intangible Assets [Line Items]
Number of members served, approximately (in member) \| medical_member	360,000			360,000
Premium revenue				$ 1,486,000,000
Goodwill impairment charges	$ 124,000,000
Medicaid \| New Mexico \| Health Plans
Finite-Lived Intangible Assets [Line Items]
Number of members served, approximately (in member) \| medical_member	224,000			224,000
Premium revenue				$ 1,205,000,000
Goodwill impairment charges	$ 74,000,000