Goodwill and other intangible assets (Details 1) (USD $)	Sep. 30, 2011	Dec. 31, 2010
Other intangible assets
Finite-Lived Intangible Assets, Gross	$ 2,184,200,000	$ 2,108,600,000
Finite-Lived Intangible Assets, Accumulated Amortization	(518,400,000)	(383,600,000)
Total other intangible assets	1,665,800,000	1,725,000,000
PBM [Member] | Customer Contracts [Member]
Other intangible assets
Finite-Lived Intangible Assets, Gross	2,018,400,000	2,018,700,000
Finite-Lived Intangible Assets, Accumulated Amortization	(457,500,000)	(346,400,000)
Finite-Lived Intangible Assets, Net	1,560,900,000	1,672,300,000
EM [Member] | Customer Relationships [Member]
Other intangible assets
Finite-Lived Intangible Assets, Gross	68,400,000	68,400,000
Finite-Lived Intangible Assets, Accumulated Amortization	(37,000,000)	(32,200,000)
Finite-Lived Intangible Assets, Net	31,400,000	36,200,000
PBM [Member] | Other Intangible Assets [Member]
Other intangible assets
Finite-Lived Intangible Assets, Gross	96,700,000	20,800,000
Finite-Lived Intangible Assets, Accumulated Amortization	(23,900,000)	(5,000,000)
Finite-Lived Intangible Assets, Net	72,800,000	15,800,000
EM [Member] | Other Intangible Assets [Member]
Other intangible assets
Finite-Lived Intangible Assets, Gross	700,000	700,000
Finite-Lived Intangible Assets, Accumulated Amortization	0	0
Finite-Lived Intangible Assets, Net	700,000	700,000
PBM [Member]
Other intangible assets
Finite-Lived Intangible Assets, Gross	2,115,100,000	2,039,500,000
Finite-Lived Intangible Assets, Accumulated Amortization	(481,400,000)	(351,400,000)
Finite-Lived Intangible Assets, Net	1,633,700,000	1,688,100,000
EM [Member]
Other intangible assets
Finite-Lived Intangible Assets, Gross	69,100,000	69,100,000
Finite-Lived Intangible Assets, Accumulated Amortization	(37,000,000)	(32,200,000)
Finite-Lived Intangible Assets, Net	$ 32,100,000	$ 36,900,000