Leases (Capital Leases Narrative) (Details) $ in Millions		12 Months Ended
	Dec. 22, 2016 USD ($) ft² state item	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Capital Leased Assets [Line Items]
Capital Lease Obligations Incurred		$ 31	$ 179	$ 50
Proceeds from sale-lease back			159
Capital Leases, Lessee Balance Sheet, Assets by Major Class, Accumulated Depreciation		218	240
HCP, Inc. [Member]
Capital Leased Assets [Line Items]
Number of buildings in transaction | item	10
Proceeds from sale-lease back	$ 159
Area of Real Estate Property | ft²	756,183
Number of states the buildings are located | state	5
Land and Land Improvements [Member]
Capital Leased Assets [Line Items]
Capital Leased Assets, Gross		63	69
Building and Building Improvements [Member]
Capital Leased Assets [Line Items]
Capital Leased Assets, Gross		774	826
Equipment and Fixture [Member]
Capital Leased Assets [Line Items]
Capital Leased Assets, Gross		$ 28	$ 56