SCHEDULE I-CONDENSED FINANCIAL INFORMATION OF REGISTRANT – CONDENSED STATEMENTS OF COMPREHENSIVE INCOME (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Costs and expenses:
Direct service costs and other operating expenses		$ 261,653	$ 227,372	$ 231,372	$ 221,486	$ 240,985	$ 229,094	$ 214,077	$ 192,456	$ 941,883	[1],[2],[3]	$ 876,612	[1],[2],[3]	$ 822,392	[1],[2],[3]
Interest expense		9,266	7,663	4,900	4,148	3,413	3,038	1,994	1,748	25,977		10,193		6,581
Interest and other income		(2,086)	(1,781)	(1,071)	(949)	(702)	(741)	(692)	(683)	(5,887)		(2,818)		(2,165)
Total costs and expenses		1,644,029	1,374,431	1,408,551	1,276,348	1,201,139	1,248,192	1,150,418	1,091,618	5,703,359		4,691,367		4,526,284
Income (loss) before income taxes		50,386	44,975	10,588	29,275	62,246	43,940	13,927	25,404	135,224		145,517		71,116
Benefit for income taxes		4,123	(11,739)	(5,661)	(11,806)	(26,469)	(18,631)	(12,615)	(12,013)	(25,083)		(69,728)		(42,409)
Net income attributable to Magellan		$ 54,509	$ 32,451	$ 5,500	$ 17,747	$ 35,175	$ 25,509	$ 3,958	$ 13,237	110,207		77,879		31,413
Other comprehensive income:
Unrealized (loss) gain on available-for-sale securities	[4]									(205)		87		(119)
Comprehensive income										110,002		77,966		31,294
Magellan Health, Inc.
Costs and expenses:
Direct service costs and other operating expenses										38,157		41,336		26,613
Interest expense										8,343
Interest and other income										(157)
Total costs and expenses										46,343		41,336		26,613
Income (loss) before income taxes										(46,343)		(41,336)		(26,613)
Benefit for income taxes										17,918		16,072		10,045
Net loss before equity in subsidiaries										(28,425)		(25,264)		(16,568)
Equity in earnings from subsidiaries										138,632		103,143		47,981
Net income attributable to Magellan										110,207		77,879		31,413
Other comprehensive income:
Unrealized (loss) gain on available-for-sale securities										(205)		87		(119)
Comprehensive income										$ 110,002		$ 77,966		$ 31,294

[1] Includes changes in fair value of contingent consideration of $44,257, $(104) and $696 for the years ended December 31, 2015, 2016 and 2017, respectively.

[2] Includes impairment of intangible assets of $4,800 for the year ended December 31, 2016.

[3] Includes stock compensation expense of $50,384, $37,422 and $39,116 for the years ended December 31, 2015, 2016 and 2017, respectively.

[4] Net of income tax (benefit) expense of $(68), $51 and $(8) for the years ended December 31, 2015, 2016 and 2017, respectively.