Condensed consolidating financial information (Details 2) (USD $) In Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Condensed Consolidating Statement of Cash Flows
Net cash flows provided by (used in) operating activities			$ 1,659.9	$ 1,842.0
Cash flows from investing activities:
Purchases of property and equipment	(44.0)	(33.5)	(98.1)	(84.6)
Other			8.5	5.8
Net cash used in investing activities - continuing operations			(89.6)	(78.8)
Net cash used in investing activities - discontinued operations				(0.8)
Net cash (used in) provided by investing activities			(89.6)	(79.6)
Cash flows from financing activities:
Repayment of long-term debt			(0.1)	(1,340.1)
Treasury stock acquired			(2,515.7)	(1,276.2)
Proceeds from long-term debt, net of discounts			1,494.0
Tax benefit relating to employee stock compensation			27.3	32.9
Deferred financing fees			(62.7)	(3.9)
Net proceeds from employee stock plans			28.9	19.3
Net cash used in financing activities			(1,028.3)	(2,568.0)
Effect of foreign currency translation adjustment			(3.1)	2.7
Net increase (decrease) in cash and cash equivalents			538.9	(802.9)
Cash and cash equivalents at beginning of period			523.7	1,070.4
Cash and cash equivalents at end of period	1,062.6	267.5	1,062.6	267.5
Express Scripts, Inc. [Member]
Condensed Consolidating Statement of Cash Flows
Net cash flows provided by (used in) operating activities			1,377.2	1,323.5
Cash flows from investing activities:
Purchases of property and equipment			(81.9)	(55.4)
Other				12.7
Net cash used in investing activities - continuing operations				(42.7)
Net cash (used in) provided by investing activities			(81.9)	(42.7)
Cash flows from financing activities:
Repayment of long-term debt			(0.1)	(1,340.1)
Treasury stock acquired			(2,515.7)	(1,276.2)
Proceeds from long-term debt, net of discounts			1,494.0
Tax benefit relating to employee stock compensation			27.3	32.9
Deferred financing fees			(62.7)	(3.9)
Net proceeds from employee stock plans			28.9	19.3
Net transactions with parent			261.6	476.4
Net cash used in financing activities			(766.7)	(2,091.6)
Net increase (decrease) in cash and cash equivalents			528.6	(810.8)
Cash and cash equivalents at beginning of period			456.7	1,005.0
Cash and cash equivalents at end of period	985.3	194.2	985.3	194.2
Guarantors [Member]
Condensed Consolidating Statement of Cash Flows
Net cash flows provided by (used in) operating activities			552.3	733.9
Cash flows from investing activities:
Purchases of property and equipment			(11.5)	(27.1)
Other			(1.7)	(2.0)
Net cash used in investing activities - continuing operations				(29.1)
Net cash (used in) provided by investing activities			(13.2)	(29.1)
Cash flows from financing activities:
Net transactions with parent			(542.6)	(706.7)
Net cash used in financing activities			(542.6)	(706.7)
Net increase (decrease) in cash and cash equivalents			(3.5)	(1.9)
Cash and cash equivalents at beginning of period			9.0	10.0
Cash and cash equivalents at end of period	5.5	8.1	5.5	8.1
Non-Guarantors [Member]
Condensed Consolidating Statement of Cash Flows
Net cash flows provided by (used in) operating activities			23.6	3.8
Cash flows from investing activities:
Purchases of property and equipment			(4.7)	(2.1)
Other			10.2	(4.9)
Net cash used in investing activities - continuing operations				(7.0)
Net cash used in investing activities - discontinued operations				(0.8)
Net cash (used in) provided by investing activities			5.5	(7.8)
Cash flows from financing activities:
Net transactions with parent			(12.2)	11.1
Net cash used in financing activities			(12.2)	11.1
Effect of foreign currency translation adjustment			(3.1)	2.7
Net increase (decrease) in cash and cash equivalents			13.8	9.8
Cash and cash equivalents at beginning of period			58.0	55.4
Cash and cash equivalents at end of period	71.8	65.2	71.8	65.2
Eliminations [Member]
Condensed Consolidating Statement of Cash Flows
Net cash flows provided by (used in) operating activities			(293.2)	(219.2)
Cash flows from financing activities:
Net transactions with parent			293.2	219.2
Net cash used in financing activities			293.2	219.2
Cash and cash equivalents at beginning of period			0
Cash and cash equivalents at end of period	$ 0		$ 0