Contingencies and Certain Commitments (Details) - USD ($) $ / shares in Units, shares in Millions	Sep. 07, 2018	Mar. 14, 2018	Mar. 12, 2018	Sep. 30, 2018	Apr. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Share repurchase agreement, amount			$ 4,000,000,000
Accelerated share repurchases, cash paid		$ 4,000,000,000
Shares repurchased	21	87
Accelerated share repurchase, average price paid for all shares delivered (in dollars per share)	$ 36.86
Shares repurchased, price per share (in dollars per share)		$ 36.61
Shares received in initial delivery, percentage of agreement amount			80.00%
Remaining authorized repurchase amount				$ 9,200,000,000
Office Building In Hudson Yards Neighborhood Of New York City [Member]
Property Subject to or Available for Operating Lease [Line Items]
Term of corporate headquarters lease agreement					20 years
Future minimum commitment for corporate headquarters lease					$ 1,700,000,000