SCHEDULE I-CONDENSED FINANCIAL INFORMATION OF REGISTRANT – CONDENSED STATEMENTS OF CASH FLOWS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net cash used in operating activities	$ 162,273	$ 66,699	$ 157,457
Cash flows from investing activities:
Net cash provided by (used in) investing activities	(316,390)	(244,339)	(193,187)
Cash flows from financing activities:
Proceeds from issuance of debt	1,041,736	375,000
Proceeds from exercise of stock options	44,355	25,145	53,493
Payments to acquire treasury stock	(21,765)	(106,806)	(206,044)
Other	(9,560)	1,230	409
Net cash (used in) provided by financing activities	248,341	233,119	(185,869)
Net (decrease) increase in cash and cash equivalents	94,224	55,479	(221,599)
Cash and cash equivalents at beginning of period	304,508	249,029	470,628
Cash and cash equivalents at end of period	398,732	304,508	249,029
Magellan Health, Inc.
Cash flows from operating activities:
Net cash used in operating activities	(21,778)	(24,283)	(17,390)
Cash flows from investing activities:
Dividends received from/(capital contributions to) subsidiaries, net	(836,396)	106,235	166,442
Net cash provided by (used in) investing activities	(836,396)	106,235	166,442
Cash flows from financing activities:
Proceeds from issuance of debt	841,736
Proceeds from exercise of stock options	44,355	24,547	54,091
Payments to acquire treasury stock	(21,765)	(106,806)	(204,427)
Payments on debt	(4,375)
Other	(1,777)	307	1,284
Net cash (used in) provided by financing activities	858,174	(81,952)	(149,052)
Cash and cash equivalents at beginning of period	2	2	2
Cash and cash equivalents at end of period	$ 2	$ 2	$ 2