Organization (Details) £ in Millions, shares in Millions		12 Months Ended
	Dec. 31, 2014 GBP (£) segment shares	Aug. 31, 2017 segment
Schedule of Equity Method Investments [Line Items]
Number of reportable segments | segment	3	3
Common stock conversion ratio		1
Walgreens Boots Alliance
Schedule of Equity Method Investments [Line Items]
Increased ownership percentage of Alliance Boots	55.00%
Total purchase price cash consideration | £	£ 3,133
Number of shares exchanged in acquisition (in shares) | shares	144.3