SCHEDULE I-CONDENSED FINANCIAL INFORMATION OF REGISTRANT – CONDENSED BALANCE SHEETS (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current Assets:
Cash and cash equivalents	$ 398,732	$ 304,508	$ 249,029	$ 470,628
Accounts receivable	660,775	606,764	428,644
Other current assets	72,323	51,507
Total Current Assets	1,483,353	1,319,267
Total Assets	2,957,234	2,443,687
LIABILITIES AND STOCKHOLDERS' EQUITY
Accrued liabilities	193,635	202,176
Total Current Liabilities	892,303	1,092,850
Total Liabilities	1,680,740	1,339,198
Preferred stock, par value $.01 per share Authorized—10,000 shares at December 31, 2016 and December 31, 2017-Issued and outstanding-none
Ordinary common stock, par value $.01 per share Authorized-100,000 shares at December 31, 2016 and December 31, 2017-Issued and outstanding-51,993 and 23,517 shares at December 31, 2016, respectively, and 52,973 and 24,202 shares at December 31, 2017, respectively	530	520
Other Stockholders' Equity:
Additional paid-in capital	1,274,811	1,186,283
Retained earnings	1,399,495	1,289,288
Accumulated other comprehensive loss	(380)	(175)
Treasury stock, at cost, 28,476 and 28,771 shares at December 31, 2016 and December 31, 2017, respectively	(1,397,962)	(1,376,197)
Total Stockholders' Equity	1,276,494	1,099,719
Total Liabilities, Redeemable Non-Controlling Interest and Stockholders' Equity	2,957,234	2,443,687
Magellan Health, Inc.
Current Assets:
Cash and cash equivalents	2	2	$ 2	$ 2
Accounts receivable	157
Due from affiliates, net	283,802
Other current assets	32
Total Current Assets	283,993	2
Investment in subsidiaries	1,830,555	1,206,555
Total Assets	2,114,548	1,206,557
LIABILITIES AND STOCKHOLDERS' EQUITY
Accrued liabilities	7,227	496
Due to affiliates, net		106,342
Current debt	108,881
Total Current Liabilities	116,108	106,838
Long-term debt	721,946
Total Liabilities	838,054	106,838
Preferred stock, par value $.01 per share Authorized—10,000 shares at December 31, 2016 and December 31, 2017-Issued and outstanding-none
Ordinary common stock, par value $.01 per share Authorized-100,000 shares at December 31, 2016 and December 31, 2017-Issued and outstanding-51,993 and 23,517 shares at December 31, 2016, respectively, and 52,973 and 24,202 shares at December 31, 2017, respectively	530	520
Other Stockholders' Equity:
Additional paid-in capital	1,274,811	1,186,283
Retained earnings	1,399,495	1,289,288
Accumulated other comprehensive loss	(380)	(175)
Treasury stock, at cost, 28,476 and 28,771 shares at December 31, 2016 and December 31, 2017, respectively	(1,397,962)	(1,376,197)
Total Stockholders' Equity	1,276,494	1,099,719
Total Liabilities, Redeemable Non-Controlling Interest and Stockholders' Equity	$ 2,114,548	$ 1,206,557