Cash Paid For Settlement Of Conversion Option

No definition available.

Name:	moh_CashPaidForSettlementOfConversionOption
Namespace Prefix:	moh_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The value of the financial instrument(s) that the original debt is being converted into in a noncash (or part noncash) transaction. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.

+ References

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-Name Accounting Standards Codification
-Topic 230
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+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The number of shares issued in exchange for the original debt being converted in a noncash (or part noncash) transaction. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or payments in the period.

+ References

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 20
-Section 50
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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The price per share of the conversion feature embedded in the debt instrument.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 5
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-URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6031898-161870

+ Details

Name:	us-gaap_DebtInstrumentConvertibleConversionPrice1
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Ratio applied to the conversion of debt instrument into equity with equity shares divided by debt principal amount.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
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+ Details

Name:	us-gaap_DebtInstrumentConvertibleConversionRatio1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount by which the convertible debt's if-converted value exceeds its principle amount at the balance sheet date, regardless of whether the instrument is currently convertible. This element applies to public companies only.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 5
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6031898-161870

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Remaining amortization period for discount on the liability component of convertible debt which may be settled in cash upon conversion, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

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Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

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+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
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+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- 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.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of the required periodic payments applied to principal.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The cash outflow during the period from the repayment of aggregate short-term and long-term debt. Excludes payment of capital lease obligations.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
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Namespace Prefix:	us-gaap_
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Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_DebtInstrumentAxis=moh_CashConvertibleSeniorNotesDue2020Member
Namespace Prefix:
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Balance Type:
Period Type:

- Details

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Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=moh_A4.875SeniorNotesMember
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Balance Type:
Period Type:

- Details

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Namespace Prefix:
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Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_LineOfCreditMember
Namespace Prefix:
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Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_LetterOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
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- Details

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Debt - Additional Information (Details) $ / shares in Units, shares in Millions	1 Months Ended			3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018 USD ($) $ / shares	Mar. 31, 2018 shares	Dec. 31, 2017 USD ($)	Sep. 30, 2018 USD ($) $ / shares shares	Jun. 30, 2018 USD ($)	Sep. 30, 2018 USD ($) $ / shares	Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)	May 31, 2018 USD ($)	Jun. 06, 2017 USD ($)	Jan. 31, 2017 USD ($)
Debt Instrument [Line Items]
Aggregate principal amount of notes outstanding	$ 1,344,000,000			$ 1,344,000,000		$ 1,344,000,000
Cash paid for partial settlement of conversion option						477,000,000	$ 0
Debt conversion				$ 37,000,000	$ 21,000,000
Loss on debt extinguishment						$ 25,000,000	$ 0
1.125% Notes
Debt Instrument [Line Items]
Percentage of contractual interest rate on Notes	1.125%			1.125%		1.125%
Senior Notes \| 4.875% Notes
Debt Instrument [Line Items]
Aggregate principal amount of notes outstanding	$ 330,000,000			$ 330,000,000		$ 330,000,000
Face amount										$ 330,000,000
Percentage of contractual interest rate on Notes	4.875%			4.875%		4.875%				4.875%
Senior Notes \| 5.375% Notes
Debt Instrument [Line Items]
Aggregate principal amount of notes outstanding	$ 700,000,000			$ 700,000,000		$ 700,000,000
Percentage of contractual interest rate on Notes	5.375%			5.375%		5.375%
Line of Credit \| Credit Facility
Debt Instrument [Line Items]
Maximum borrowing capacity											$ 500,000,000
Term of debt instrument						5 years
Aggregate principal amount of notes outstanding									$ 300,000,000
Current borrowing capacity	$ 494,000,000			$ 494,000,000		$ 494,000,000
Line of Credit \| Letter of Credit
Debt Instrument [Line Items]
Amount outstanding under Letter of Credit	6,000,000			6,000,000		6,000,000
Convertible Notes \| 1.125% Notes
Debt Instrument [Line Items]
Aggregate principal amount of notes outstanding	$ 314,000,000			$ 314,000,000		$ 314,000,000
Percentage of contractual interest rate on Notes	1.125%		1.125%	1.125%		1.125%		1.125%
Repayments of principal				$ 140,000,000	96,000,000
Repayments of debt				483,000,000	228,000,000
Cash paid for partial settlement of conversion option				$ 343,000,000	$ 132,000,000
Conversion ratio						0.0245277
Conversion price per share of common stock (in dollars per share) \| $ / shares	$ 40.77			$ 40.77		$ 40.77
Effective interest percentage	6.00%			6.00%		6.00%
Remaining amortization period						1 year 4 months
If-converted value						$ 626,000,000		$ 406,000,000
Loss on debt extinguishment				$ 10,000,000		15,000,000
Convertible Notes \| 1.625% Notes (2)
Debt Instrument [Line Items]
Aggregate principal amount of notes outstanding	$ 64,000,000			$ 64,000,000		$ 64,000,000
Percentage of contractual interest rate on Notes	1.625%			1.625%		1.625%
Debt conversion	$ 64,000,000		$ 97,000,000
Debt conversion (in shares) \| shares		1.8		0.6
Conversion ratio						0.0172157
Conversion price per share of common stock (in dollars per share) \| $ / shares	$ 58.09			$ 58.09		$ 58.09
Loss on debt extinguishment						$ 10,000,000