Business Segment Information (Details) (USD $) In Thousands, unless otherwise specified	1 Months Ended	3 Months Ended								12 Months Ended
	Sep. 30, 2010 customer	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Operating results by business segment
Number of customers subcontracted by Public Sector with Medicaid Administration	1
Managed care and other revenue		$ 742,950	$ 711,092	$ 716,998	$ 686,059	$ 652,804	$ 625,079	$ 641,742	$ 632,366	$ 2,857,099	$ 2,551,991	$ 2,734,406
Dispensing Revenue		87,324	87,345	88,475	87,154	68,660	61,764	56,596	60,389	350,298	247,409	234,834
Cost of care		(528,529)	(516,238)	(521,830)	(505,293)	(461,527)	(448,051)	(441,446)	(433,700)	(2,071,890)	(1,784,724)	(1,907,985)
Cost of goods sold		(82,859)	(81,662)	(82,855)	(81,038)	(64,479)	(57,636)	(53,404)	(56,519)	(328,414)	(232,038)	(218,630)
Direct service costs and other										(557,512)	(529,634)	(566,582)
Stock compensation expense										17,783	17,418	15,102
Segment profit (loss)										267,364	270,422	291,145
Identifiable assets by business segment
Restricted cash		226,554				185,794				226,554	185,794	116,734
Net accounts receivable		138,253				121,606				138,253	121,606	106,934
Investments		233,690				200,903				233,690	200,903	284,504
Goodwill		426,939				426,939				426,939	426,939	426,939
Commercial
Operating results by business segment
Managed care and other revenue										728,512	561,780	652,221
Cost of care										(437,518)	(314,178)	(365,115)
Direct service costs and other										(172,035)	(152,760)	(156,278)
Stock compensation expense										532	839	714
Segment profit (loss)										119,491	95,681	131,542
Identifiable assets by business segment
Restricted cash		18,254				18,319				18,254	18,319	22,501
Net accounts receivable		39,678				26,822				39,678	26,822	26,564
Investments		21,273				5,320				21,273	5,320	8,507
Goodwill		120,485				120,485				120,485	120,485	120,485
Public Sector
Operating results by business segment
Managed care and other revenue										1,620,875	1,459,659	1,442,093
Cost of care										(1,413,320)	(1,271,532)	(1,246,779)
Direct service costs and other										(89,129)	(67,227)	(67,577)
Stock compensation expense										1,111	872	714
Segment profit (loss)										119,537	121,772	128,451
Identifiable assets by business segment
Restricted cash		147,766				164,479				147,766	164,479	82,813
Net accounts receivable		27,415				28,331				27,415	28,331	15,086
Investments		101,093				131,261				101,093	131,261	183,632
Radiology Benefits Management
Operating results by business segment
Managed care and other revenue										349,133	344,335	454,105
Cost of care										(228,383)	(205,240)	(298,516)
Direct service costs and other										(55,418)	(61,681)	(67,672)
Stock compensation expense										1,567	1,563	1,485
Segment profit (loss)										66,899	78,977	89,402
Identifiable assets by business segment
Restricted cash												7,890
Net accounts receivable		7,580				1,398				7,580	1,398	2,496
Investments												5,005
Goodwill		104,549				104,549				104,549	104,549	104,549
Specialty Pharmaceutical Management
Operating results by business segment
Managed care and other revenue										55,178	48,534	35,812
Dispensing Revenue										350,298	247,409	234,834
Cost of goods sold										(328,414)	(232,038)	(218,630)
Direct service costs and other										(26,709)	(24,344)	(26,368)
Stock compensation expense										672	693	424
Segment profit (loss)										51,025	40,254	26,072
Identifiable assets by business segment
Net accounts receivable		44,975				21,370				44,975	21,370	28,309
Goodwill		142,291				142,291				142,291	142,291	142,291
Medicaid Administration
Operating results by business segment
Managed care and other revenue										172,491	220,453	176,283
Cost of care										(61,759)	(76,544)	(23,683)
Direct service costs and other										(84,884)	(103,254)	(124,312)
Stock compensation expense										335	124	74
Segment profit (loss)										26,183	40,779	28,362
Identifiable assets by business segment
Net accounts receivable		20,780				30,654				20,780	30,654	29,632
Goodwill		59,614				59,614				59,614	59,614	59,614
Corporate and Elimination
Operating results by business segment
Managed care and other revenue										(69,090)	(82,770)	(26,108)
Cost of care										69,090	82,770	26,108
Direct service costs and other										(129,337)	(120,368)	(124,375)
Stock compensation expense										13,566	13,327	11,691
Segment profit (loss)										(115,771)	(107,041)	(112,684)
Identifiable assets by business segment
Restricted cash		60,534				2,996				60,534	2,996	3,530
Net accounts receivable		(2,175)				13,031				(2,175)	13,031	4,847
Investments		$ 111,324				$ 64,322				$ 111,324	$ 64,322	$ 87,360