Net Income per Common Share Attributable to Magellan Helath, Inc (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Numerator:
Net income attributable to Magellan	$ 5,500	$ 3,958	$ 23,247	$ 17,195
Denominator:
Weighted average number of common shares outstanding-basic (in shares)	23,108	23,516	23,060	23,570
Common stock equivalents-stock options (in shares)	399	383	436	318
Common stock equivalents-RSAs (in shares)	439	681	421	622
Common stock equivalents-RSUs (in shares)	30	27	56	27
Common stock equivalents- PSUs( in shares)	61	34	62	35
Common stock equivalents-employee stock purchase plan (in shares)	1	2	2	2
Weighted average number of common shares outstanding-diluted (in shares)	24,038	24,643	24,037	24,574
Net income attributable to Magellan per common share-basic (in dollars per share)	$ 0.24	$ 0.17	$ 1.01	$ 0.73
Net income attributable to Magellan per common share-diluted (in dollars per share)	$ 0.23	$ 0.16	$ 0.97	$ 0.70
Potential dilutive securities excluded from computation of dilutive securities (in shares)	800	1,200	700	1,100