Selected Quarterly Financial Data (Unaudited) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Net revenue:
Managed care and other	$ 753,489	$ 703,020	$ 682,274	$ 829,591	$ 823,627	$ 770,113	$ 746,720	$ 722,589	$ 2,968,374		$ 3,063,049		$ 2,857,099
PBM and dispensing	228,970	220,150	205,740	136,884	184,583	103,485	96,028	99,172	791,744		483,268		350,298
Total net revenue	982,459	923,170	888,014	966,475	1,008,210	873,598	842,748	821,761	3,760,118		3,546,317		3,207,397
Cost and expenses:
Cost of care	506,090	495,180	481,617	605,708	605,782	564,537	537,630	525,027	2,088,595		2,232,976		2,071,890
Cost of goods sold	212,905	202,180	192,566	125,298	174,411	97,503	90,175	93,512	732,949		455,601		328,414
Direct service costs and other operating expenses (1)	202,814	176,928	179,034	164,722	178,588	156,834	144,497	139,627	723,498	[1]	619,546	[1]	557,512	[1]
Depreciation and amortization	24,405	23,956	22,480	20,229	21,224	17,654	16,946	16,170	91,070		71,994		60,488
Interest expense	1,668	2,879	2,004	836	809	789	792	610	7,387		3,000		2,247
Interest and other income	(474)	(241)	(275)	(311)	(983)	(291)	(358)	(353)	(1,301)		(1,985)		(2,019)
Total costs and expenses	947,408	900,882	877,426	916,482	979,831	837,026	789,682	774,593	3,642,198		3,381,132		3,018,532
Income before income taxes	35,051	22,288	10,588	49,993	28,379	36,572	53,066	47,168	117,920		165,185		188,865
Provision for income taxes	15,305	(3,490)	6,261	25,613	9,888	(10,660)	21,586	19,110	43,689		39,924		37,838
Net income	19,746	25,778	4,327	24,380	18,491	47,232	31,480	28,058	74,231		125,261		151,027
Less: net income (loss) attributable to non-controlling interest	(1,819)	(1,355)	(659)	(1,340)					(5,173)
Net income attributable to Magellan Health, Inc.	21,565	27,133	4,986	25,720					79,404		125,261		151,027
Weighted average number of common shares outstanding-basic	25,558	26,703	27,144	27,370	27,285	26,990	26,829	27,110	26,689		27,054		27,386
Weighted average number of common shares outstanding-diluted	26,382	27,242	27,765	28,051	28,008	27,704	27,338	27,648	27,355		27,675		27,882
Net income per common share-basic:	$ 0.84	$ 1.02	$ 0.18	$ 0.94	$ 0.68	$ 1.75	$ 1.17	$ 1.03	$ 2.98		$ 4.63		$ 5.51
Net income per common share-diluted:	$ 0.82	$ 1.00	$ 0.18	$ 0.92	$ 0.67	$ 1.70	$ 1.15	$ 1.01	$ 2.90		$ 4.53		$ 5.42
Stock compensation expense	$ 14,601	$ 11,961	$ 9,550	$ 4,472	$ 6,488	$ 4,524	$ 4,602	$ 5,638	$ 40,584		$ 21,252		$ 17,783

[1] Includes stock compensation expense of $17,783, $21,252 and $40,584 for the years ended December 31, 2012, 2013 and 2014, respectively.