Acquisitions (Details) (USD $)	12 Months Ended	0 Months Ended		12 Months Ended	0 Months Ended	8 Months Ended	0 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Oct. 01, 2013	Dec. 31, 2013	Apr. 30, 2014	Dec. 31, 2014	Jul. 01, 2014	Dec. 31, 2012	May 17, 2013
Assets acquired
Goodwill	$ 566,106,000	$ 488,206,000		$ 488,206,000		$ 566,106,000		$ 426,939,000
Acquisition disclosures
Fair value of the contingent consideration	58,153,000					58,153,000
Changes in fair value	9,304,000
AlphaCare
Acquisitions
Amount of common stock purchased	2,200,000
AlphaCare | Measurement Period Adjustments
Acquisitions
Increase (decrease) in deferred tax liability		1,000,000
Partners Rx
Acquisitions
Amount of consideration paid in cash			99,300,000
Reduction to consideration paid due to net receipts received for working capital adjustments			700,000
Increase (decrease) in deferred tax liability	(300,000)
Acquisition disclosures
Vesting period of restricted stock issued			3 years
AlphaCare Holdings Inc.
Acquisitions
Percentage of equity interest acquired		65.00%		65.00%
Amount of additional Preferred Stock purchased	8,900,000
Percentage of ownership held	75.00%					75.00%
Voting interest of remaining shareholders	25.00%					25.00%
Assets acquired
Current assets		14,218,000		14,218,000
Property and equipment, net		271,000		271,000
Other assets		541,000		541,000
Other identified intangible assets		7,190,000		7,190,000
Goodwill		20,879,000		20,879,000
Total assets acquired		43,099,000		43,099,000
Liabilities assumed
Current liabilities		4,178,000		4,178,000
Deferred tax liabilities		2,867,000		2,867,000
Total liabilities assumed		7,045,000		7,045,000
Net assets acquired		36,054,000		36,054,000
Less: net assets attributable to noncontrolling interest		(10,554,000)		(10,554,000)
Net consideration		25,500,000		25,500,000
AlphaCare Holdings Inc. | Cash
Assets acquired
Current assets		6,249,000		6,249,000
AlphaCare Holdings Inc. | Restricted cash
Assets acquired
Current assets		7,900,000		7,900,000
AlphaCare Holdings Inc. | Initial Amounts Recognized at Acquisition Date
Assets acquired
Current assets		14,766,000		14,766,000
Property and equipment, net		310,000		310,000
Other assets		475,000		475,000
Other identified intangible assets		4,590,000		4,590,000
Goodwill		20,882,000		20,882,000
Total assets acquired		41,023,000		41,023,000
Liabilities assumed
Current liabilities		3,139,000		3,139,000
Deferred tax liabilities		1,830,000		1,830,000
Total liabilities assumed		4,969,000		4,969,000
Net assets acquired		36,054,000		36,054,000
Less: net assets attributable to noncontrolling interest		(10,554,000)		(10,554,000)
Net consideration		25,500,000		25,500,000
AlphaCare Holdings Inc. | Measurement Period Adjustments
Assets acquired
Current assets		(548,000)		(548,000)
Property and equipment, net		(39,000)		(39,000)
Other assets		66,000		66,000
Other identified intangible assets		2,600,000		2,600,000
Goodwill		(3,000)		(3,000)
Total assets acquired		2,076,000		2,076,000
Liabilities assumed
Current liabilities		1,039,000		1,039,000
Deferred tax liabilities		1,037,000		1,037,000
Total liabilities assumed		2,076,000		2,076,000
Other net changes		(1,600,000)		(1,600,000)
AlphaCare Holdings Inc. | Measurement Period Adjustments | Customer contracts
Assets acquired
Other identified intangible assets		2,600,000		2,600,000
AlphaCare Holdings Inc. | AlphaCare
Acquisitions
Equity interest held (as a percent)									7.00%
Equity investment in preferred membership units									2,000,000
Amount previously loaned to acquiree pursuant to a promissory note									5,900,000
Amount of additional Preferred Stock purchased				17,400,000
CDMI
Acquisitions
Amount of consideration paid in cash					201,100,000
Reduction to consideration paid due to net receipts received for working capital adjustments					3,900,000
Assets acquired
Current assets					41,996,000
Property and equipment, net					457,000
Other assets					9,000
Other identified intangible assets					84,220,000
Goodwill					69,092,000
Total assets acquired					195,774,000
Liabilities assumed
Current liabilities					28,985,000
Contingent consideration	45,778,000				45,778,000	45,778,000
Total liabilities assumed					74,763,000
Net assets acquired					121,011,000
Acquisition disclosures
Amount to be reinvested in restricted common stock by the principal owners and certain key management of acquired entity					80,000,000
Vesting period of restricted stock issued					42 months
Maximum potential contingent payments					165,000,000
Total revenue						31,500,000
Segment Profit						27,200,000
Identified intangible assets					84,200,000
Working capital receivable	100,000					100,000
Estimated undiscounted future contingent payments	65,700,000				61,700,000	65,700,000
Fair value of the contingent consideration	54,900,000					54,900,000
Acquisition related costs	1,300,000
Net revenue	3,771,711,000			3,588,975,000
Net income	75,530,000			114,549,000
Income per share attributable to Magellan Health Services, Inc.:
Basic (in dollars per share)	$ 2.83			$ 4.23
Diluted (in dollars per share)	$ 2.75			$ 4.12
CDMI | Accounts receivable
Assets acquired
Current assets					41,892,000
CDMI | Customer contracts
Acquisition disclosures
Identified intangible assets					82,800,000
Period of amortization of intangible assets acquired					8 years
CDMI | Tradenames
Acquisition disclosures
Identified intangible assets					400,000
Period of amortization of intangible assets acquired					20 months
CDMI | Non-compete agreements
Acquisition disclosures
Identified intangible assets					1,000,000
Period of amortization of intangible assets acquired					6 years 6 months
Cobalt
Acquisitions
Amount of consideration paid in cash							8,000,000
Liabilities assumed
Contingent consideration	3,071,000					3,071,000
Acquisition disclosures
Maximum potential contingent payments							6,000,000
Estimated undiscounted future contingent payments	$ 4,200,000					$ 4,200,000	$ 4,200,000