Acquisitions (Details) (USD $)	3 Months Ended	9 Months Ended			0 Months Ended	9 Months Ended							0 Months Ended		1 Months Ended	3 Months Ended		5 Months Ended	9 Months Ended			1 Months Ended			0 Months Ended
	Sep. 30, 2014	Sep. 30, 2014	Dec. 31, 2013	Dec. 31, 2012	Oct. 01, 2013 Partners Rx	Sep. 30, 2014 Partners Rx	Dec. 31, 2013 AlphaCare Holdings Inc.	Dec. 31, 2013 AlphaCare Holdings Inc. Cash	Dec. 31, 2013 AlphaCare Holdings Inc. Restricted cash	Dec. 31, 2013 AlphaCare Holdings Inc. Initial Amounts Recognized at Acquisition Date	Dec. 31, 2013 AlphaCare Holdings Inc. Measurement Period Adjustments	Dec. 31, 2013 AlphaCare Holdings Inc. Measurement Period Adjustments Customer contracts	Dec. 31, 2013 AlphaCare Holdings Inc. AlphaCare	May 17, 2013 AlphaCare Holdings Inc. AlphaCare	Apr. 30, 2014 CDMI	Sep. 30, 2014 CDMI	Sep. 30, 2013 CDMI	Sep. 30, 2014 CDMI	Sep. 30, 2014 CDMI	Sep. 30, 2013 CDMI	Apr. 30, 2014 CDMI Accounts receivable	Apr. 30, 2014 CDMI Customer contracts	Apr. 30, 2014 CDMI Tradenames	Apr. 30, 2014 CDMI Non-compete agreements	Jul. 01, 2014 Cobalt	Sep. 30, 2014 Cobalt	Jul. 01, 2014 Cobalt
Acquisitions
Amount of consideration paid in cash					$ 97,300,000										$ 205,000,000										$ 7,900,000
Reduction to consideration paid due to net receipts received for working capital adjustments					700,000																				100,000
Increase (decrease) in deferred tax liability						(300,000)
Percentage of equity interest acquired							65.00%
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 Series A Preferred purchased													17,400,000
Ownership percentage							65.00%
Assets acquired
Current assets							14,218,000	6,249,000	7,900,000	14,766,000	(548,000)				42,226,000						42,123,000
Property and equipment, net							271,000			310,000	(39,000)				457,000
Other assets							541,000			475,000	66,000				9,000
Other identified intangible assets							7,190,000			4,590,000	2,600,000	2,600,000			84,220,000
Goodwill	566,106,000	566,106,000	488,206,000	426,939,000			20,879,000			20,882,000	(3,000)				69,092,000
Total assets acquired							43,099,000			41,023,000	2,076,000				196,004,000
Liabilities assumed
Current liabilities							4,178,000			3,139,000	1,039,000				29,160,000
Deferred tax liabilities							2,867,000			1,830,000	1,037,000
Contingent consideration															45,778,000	45,778,000		45,778,000	45,778,000							3,071,000
Total liabilities assumed							7,045,000			4,969,000	2,076,000				74,938,000
Net assets acquired							36,054,000			36,054,000					121,066,000
Less: net assets attributable to noncontrolling interest							(10,554,000)			(10,554,000)
Net consideration							25,500,000			25,500,000
Other net changes											(1,600,000)
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												6,000,000
Total revenue																		18,200,000
Segment Profit																		15,600,000
Identified intangible assets															84,200,000							82,800,000	400,000	1,000,000
Period of amortization of intangible assets acquired																						8 years	20 months	6 years 6 months
Working capital receivable																3,900,000		3,900,000	3,900,000
Estimated undiscounted future contingent payments															61,700,000												4,200,000
Fair value of the contingent consideration	51,981,000	51,981,000														48,800,000		48,800,000	48,800,000
Change in fair value of the contingent consideration	1,900,000	3,132,000														1,800,000			3,000,000
Acquisition related costs																			1,200,000
Net revenue																923,170,000	884,980,000		2,789,252,000	2,568,398,000
Net income																$ 27,133,000	$ 45,410,000		$ 53,965,000	$ 99,951,000
Income per share attributable to Magellan Health Services, Inc.:
Basic (in dollars per share)																$ 1.02	$ 1.68		$ 1.99	$ 3.71
Diluted (in dollars per share)																$ 1.00	$ 1.63		$ 1.94	$ 3.61