Business Segment Information (Details) (USD $) In Thousands, unless otherwise specified	1 Months Ended	3 Months Ended		9 Months Ended
	Sep. 30, 2010 customer	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Operating results by business segment
Number of customers subcontracted by Public Sector with Medicaid Administration	1
Managed care and other revenue		$ 775,957	$ 711,092	$ 2,255,748	$ 2,114,149
Dispensing revenue		97,641	87,345	282,359	262,974
Cost of care		(570,187)	(516,238)	(1,642,944)	(1,543,361)
Cost of goods sold		(91,853)	(81,662)	(265,440)	(245,555)
Direct service costs and other		(156,834)	(135,574)	(440,958)	(412,496)
Stock compensation expense		4,524	4,468	14,764	13,935
Segment profit (loss)		59,248	69,431	203,529	189,646
Commercial
Operating results by business segment
Managed care and other revenue		190,655	176,713	578,030	535,464
Cost of care		(118,022)	(100,973)	(354,520)	(323,992)
Direct service costs and other		(47,032)	(43,007)	(129,823)	(127,825)
Stock compensation expense		124	293	390	830
Segment profit (loss)		25,725	33,026	94,077	84,477
Public Sector
Operating results by business segment
Managed care and other revenue		445,260	407,265	1,266,739	1,206,289
Cost of care		(382,913)	(358,959)	(1,095,694)	(1,058,384)
Direct service costs and other		(27,826)	(22,948)	(82,403)	(66,850)
Stock compensation expense		259	278	833	835
Segment profit (loss)		34,780	25,636	89,475	81,890
Radiology Benefits Management
Operating results by business segment
Managed care and other revenue		94,125	88,126	277,118	253,809
Cost of care		(65,403)	(58,080)	(182,212)	(166,364)
Direct service costs and other		(13,990)	(14,045)	(41,224)	(41,113)
Stock compensation expense		384	419	1,275	1,179
Segment profit (loss)		15,116	16,420	54,957	47,511
Pharmacy Solutions
Operating results by business segment
Managed care and other revenue		63,008	54,421	182,418	171,846
Dispensing revenue		97,641	87,345	282,359	262,974
Cost of care		(20,940)	(13,659)	(59,075)	(47,880)
Cost of goods sold		(91,853)	(81,662)	(265,440)	(245,555)
Direct service costs and other		(32,281)	(27,565)	(93,216)	(83,532)
Stock compensation expense		198	238	898	704
Segment profit (loss)		15,773	19,118	47,944	58,557
Corporate and Elimination
Operating results by business segment
Managed care and other revenue		(17,091)	(15,433)	(48,557)	(53,259)
Cost of care		17,091	15,433	48,557	53,259
Direct service costs and other		(35,705)	(28,009)	(94,292)	(93,176)
Stock compensation expense		3,559	3,240	11,368	10,387
Segment profit (loss)		$ (32,146)	$ (24,769)	$ (82,924)	$ (82,789)