Contingencies (Health Care Cost Recovery Litigation) (Details) - Health Care Cost Recovery Actions [Member]	1 Months Ended	3 Months Ended		6 Months Ended
	Nov. 30, 1998 USD ($) state	Jun. 30, 2018 USD ($) case	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($) case	Jun. 30, 2017 USD ($)	Jul. 24, 2017 case	Jul. 22, 2016 case
Loss Contingencies [Line Items]
Number of cases pending | case						1	1
Number of states with settled litigation | state	46
State settlement agreements annual payments	$ 9,400,000,000
State settlement agreements attorney fees annual cap	$ 500,000,000
Litigation settlement		$ 1,000,000,000	$ 1,200,000,000	$ 2,000,000,000	$ 2,300,000,000
Threatened Litigation [Member] | Canada [Member]
Loss Contingencies [Line Items]
Number of cases pending | case		10		10