Net Income per Common Share Attributable to Magellan Health, Inc. (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Numerator:
Net income attributable to Magellan Health, Inc.	$ 4,986	$ 31,480	$ 30,706	$ 59,538
Denominator:
Weighted average number of common shares outstanding-basic (in shares)	27,144,000	26,829,000	27,257,000	26,968,000
Common stock equivalents-stock options (in shares)	554,000	497,000	574,000	482,000
Common stock equivalents-restricted stock (in shares)	66,000	10,000	49,000	14,000
Common stock equivalents-restricted stock units (in shares)			27,000	26,000
Common stock equivalents-employee stock purchase plan (in shares)	1,000	2,000	1,000	2,000
Weighted average number of common shares outstanding-diluted (in shares)	27,765,000	27,338,000	27,908,000	27,492,000
Net income attributable to Magellan Health, Inc. per common share-basic (in dollars per share)	$ 0.18	$ 1.17	$ 1.13	$ 2.21
Net income attributable to Magellan Health, Inc. per common share-diluted (in dollars per share)	$ 0.18	$ 1.15	$ 1.10	$ 2.17
Potential dilutive securities excluded from computation of dilutive securities (in shares)	700,000	1,200,000	500,000	1,900,000