Supplemental Condensed Consolidating Financial Information - Condensed Consolidating Balance Sheet (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 3,186	$ 2,819	$ 2,329	$ 1,539
Investments	2,524	1,758
Restricted investments	169	0
Receivables	871	974
Income taxes refundable	54	39
Due from affiliates	0	0
Prepaid expenses and other current assets	185	131
Derivative asset	522	267
Total current assets	7,511	5,988
Property, equipment, and capitalized software, net	342	454
Deferred contract costs	101	86
Goodwill and intangible assets, net	255	760	641
Restricted investments	119	110
Investments in subsidiaries	0	0
Deferred income taxes	103	10
Other assets	40	41
Total assets	8,471	7,449	6,576
Current liabilities:
Medical claims and benefits payable	2,192	1,929	1,685	1,201
Amounts due government agencies	1,542	1,202
Accounts payable and accrued liabilities	366	385
Deferred revenue	282	315
Current portion of long-term debt	653	472
Derivative liability	522	267
Total current liabilities	5,557	4,570
Long-term debt	1,516	1,173
Deferred income taxes	0	15
Other long-term liabilities	61	42
Total liabilities	7,134	5,800
Total stockholders' equity	1,337	1,649
Total liabilities and stockholders' equity	8,471	7,449
Parent Guarantor
Current assets:
Cash and cash equivalents	504	86	360	75
Investments	192	178
Restricted investments	169	0
Receivables	2	2
Income taxes refundable	16	17
Due from affiliates	148	104
Prepaid expenses and other current assets	87	58
Derivative asset	522	267
Total current assets	1,640	712
Property, equipment, and capitalized software, net	223	301
Goodwill and intangible assets, net	15	58
Investments in subsidiaries	2,306	2,609
Deferred income taxes	17	10
Total assets	4,233	3,738
Current liabilities:
Medical claims and benefits payable	3	1
Accounts payable and accrued liabilities	178	146
Current portion of long-term debt	653	472
Derivative liability	522	267
Total current liabilities	1,356	886
Deferred income taxes	0	11
Other long-term liabilities	24	19
Total liabilities	2,896	2,089
Total stockholders' equity	1,337	1,649
Total liabilities and stockholders' equity	4,233	3,738
Reportable Legal Entities \| Parent Guarantor
Current assets:
Cash and cash equivalents	504	86	360	75
Investments	192	178
Restricted investments	169
Receivables	2	2
Income taxes refundable	16	17
Due from affiliates	148	104
Prepaid expenses and other current assets	87	58
Derivative asset	522	267
Total current assets	1,640	712
Property, equipment, and capitalized software, net	223	301
Deferred contract costs	0	0
Goodwill and intangible assets, net	15	58
Restricted investments	0	0
Investments in subsidiaries	2,306	2,609
Deferred income taxes	17	10
Other assets	32	48
Total assets	4,233	3,738
Current liabilities:
Medical claims and benefits payable	3	1
Amounts due government agencies	0	0
Accounts payable and accrued liabilities	178	146
Deferred revenue	0	0
Current portion of long-term debt	653	472
Derivative liability	522	267
Total current liabilities	1,356	886
Long-term debt	1,516	1,173
Deferred income taxes	0	11
Other long-term liabilities	24	19
Total liabilities	2,896	2,089
Total stockholders' equity	1,337	1,649
Total liabilities and stockholders' equity	4,233	3,738
Reportable Legal Entities \| Other Guarantors
Current assets:
Cash and cash equivalents	28	6	13	13
Investments	0	0
Restricted investments	0
Receivables	30	34
Income taxes refundable	(8)	4
Due from affiliates	(6)	(5)
Prepaid expenses and other current assets	22	30
Derivative asset	0	0
Total current assets	66	69
Property, equipment, and capitalized software, net	33	46
Deferred contract costs	101	86
Goodwill and intangible assets, net	43	73
Restricted investments	0	0
Investments in subsidiaries	82	246
Deferred income taxes	0	0
Other assets	2	3
Total assets	327	523
Current liabilities:
Medical claims and benefits payable	0	0
Amounts due government agencies	1	0
Accounts payable and accrued liabilities	40	34
Deferred revenue	49	40
Current portion of long-term debt	0	0
Derivative liability	0	0
Total current liabilities	90	74
Long-term debt	0	0
Deferred income taxes	15	39
Other long-term liabilities	2	1
Total liabilities	107	114
Total stockholders' equity	220	409
Total liabilities and stockholders' equity	327	523
Reportable Legal Entities \| Non-Guarantors
Current assets:
Cash and cash equivalents	2,654	2,727	1,956	1,451
Investments	2,332	1,580
Restricted investments	0
Receivables	839	938
Income taxes refundable	46	18
Due from affiliates	(142)	(99)
Prepaid expenses and other current assets	92	43
Derivative asset	0	0
Total current assets	5,821	5,207
Property, equipment, and capitalized software, net	86	107
Deferred contract costs	0	0
Goodwill and intangible assets, net	197	629
Restricted investments	119	110
Investments in subsidiaries	0	0
Deferred income taxes	101	0
Other assets	7	6
Total assets	6,331	6,059
Current liabilities:
Medical claims and benefits payable	2,189	1,928
Amounts due government agencies	1,541	1,202
Accounts payable and accrued liabilities	148	205
Deferred revenue	233	275
Current portion of long-term debt	16	0
Derivative liability	0	0
Total current liabilities	4,127	3,610
Long-term debt	0	16
Deferred income taxes	0	(35)
Other long-term liabilities	36	22
Total liabilities	4,163	3,613
Total stockholders' equity	2,168	2,446
Total liabilities and stockholders' equity	6,331	6,059
Eliminations
Current assets:
Cash and cash equivalents	0	0	$ 0	$ 0
Investments	0	0
Restricted investments	0
Receivables	0	0
Income taxes refundable	0	0
Due from affiliates	0	0
Prepaid expenses and other current assets	(16)	0
Derivative asset	0	0
Total current assets	(16)	0
Property, equipment, and capitalized software, net	0	0
Deferred contract costs	0	0
Goodwill and intangible assets, net	0	0
Restricted investments	0	0
Investments in subsidiaries	(2,388)	(2,855)
Deferred income taxes	(15)	0
Other assets	(1)	(16)
Total assets	(2,420)	(2,871)
Current liabilities:
Medical claims and benefits payable	0	0
Amounts due government agencies	0	0
Accounts payable and accrued liabilities	0	0
Deferred revenue	0	0
Current portion of long-term debt	(16)	0
Derivative liability	0	0
Total current liabilities	(16)	0
Long-term debt	0	(16)
Deferred income taxes	(15)	0
Other long-term liabilities	(1)	0
Total liabilities	(32)	(16)
Total stockholders' equity	(2,388)	(2,855)
Total liabilities and stockholders' equity	$ (2,420)	$ (2,871)

Medical Premium Liability Due to Agency

No definition available.

Name:	moh_MedicalPremiumLiabilityDueToAgency
Namespace Prefix:	moh_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Sum of the carrying values as of the balance sheet date of obligations incurred through that date and due within one year (or the operating cycle, if longer), including liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received, taxes, interest, rent and utilities, accrued salaries and bonuses, payroll taxes and fringe benefits.