Summary of Significant Accounting Policies (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Net revenues
Projected ACA fees									$ 25,000,000
Managed Care Revenue										2,700,000,000	2,500,000,000	2,200,000,000
Fee-For-Service and Cost-Plus Contracts Revenue										215,100,000	151,400,000	174,500,000
Block Grant Revenues										131,500,000	124,800,000	114,400,000
Performance-Based Revenue										14,000,000	25,400,000	26,500,000
Rebate Revenues										34,800,000	40,200,000	32,800,000
PBM Revenue										106,700,000
Dispensing Revenue										376,600,000	350,300,000	247,400,000
Significant customers
Revenues generated	1,008,210,000	873,598,000	842,748,000	821,761,000	830,274,000	798,437,000	805,473,000	773,213,000		3,546,317,000	3,207,397,000	2,799,400,000
Contract shutdown costs										6,100,000
Maricopa County Regional Behavioral Health Authority
Significant customers
Number of members receiving behavioral healthcare management and other related services										660,000
Termination notice										10 days
Termination notice period without cause										30 days
Revenues generated										755,000,000	758,300,000	779,500,000
Maricopa County Regional Behavioral Health Authority | Service
Significant customers
Major customer defined (as a percent)										10.00%	10.00%	10.00%
Magellan Complete Care of Arizona, Inc.
Significant customers
Percentage of investment in joint venture	80.00%									80.00%
Vanguard/Phoenix Health Plan | Magellan Complete Care of Arizona, Inc.
Significant customers
Percentage of investment in joint venture	20.00%									20.00%
Commercial | Customer A | Service
Significant customers
Revenues generated										207,080,000	192,415,000	171,109,000
Commercial | Customer B | Service
Significant customers
Revenues generated										71,085,000	67,959,000	67,049,000
Commercial | Customer C | Service
Significant customers
Revenues generated										74,203,000	118,351,000	111,607,000
Minimum number of contracts per customer										1
Revenues related to terminated contract											50,000,000
Commercial | Customer D | Service
Significant customers
Revenues generated										141,444,000	134,885,000
Public Sector | Customer E | Service
Significant customers
Revenues generated										321,072,000	240,224,000	191,063,000
Number of contract extensions available under option										1
Contract extension period available under option										1 year
Specialty Solutions | Customer F | Service
Significant customers
Revenues generated										130,895,000	117,739,000	134,257,000
Specialty Solutions | Customer G | Service
Significant customers
Revenues generated												38,297,000
Minimum number of contracts per customer										1
Specialty Solutions | Customer H | Service
Significant customers
Revenues generated										55,078,000	60,094,000	55,197,000
Specialty Solutions | Customer I | Service
Significant customers
Revenues generated										61,838,000	57,455,000	36,293,000
Specialty Solutions | Customer J | Service
Significant customers
Revenues generated										47,311,000	38,366,000	32,342,000
Pharmacy Management | Customer B | Service
Significant customers
Revenues generated										92,647,000	73,785,000	22,899,000
Minimum number of contracts per customer										1
Pharmacy Management | Customer K | Service
Significant customers
Revenues generated										133,724,000	129,209,000	90,563,000
Minimum number of contracts per customer										1
Pharmacy Management | Customer L | Service
Significant customers
Revenues generated										59,125,000	60,350,000	56,115,000
Pharmacy Management | Customer M | Service
Significant customers
Revenues generated										$ 66,153,000	$ 69,090,000	$ 82,770,000