Interim Financial Data - Impact on Consolidated Balance Sheet for the Adoption of Revenue Recognition (Details) - USD ($) $ in Millions	Dec. 31, 2018	Apr. 01, 2018	Mar. 31, 2018
ASSETS
Other assets	$ 2,160		$ 1,614
LIABILITIES AND SHAREHOLDER’S EQUITY
Deferred income taxes	5,459		5,326
Other liabilities	4,454		3,987
Retained earnings	12,370		$ 11,992
Accounting Standards Update 2014-09 [Member]
ASSETS
Other assets		$ 1,687
LIABILITIES AND SHAREHOLDER’S EQUITY
Deferred income taxes		5,290
Other liabilities		4,206
Retained earnings		11,882
Effect of Adoption [Member] | Accounting Standards Update 2014-09 [Member]
ASSETS
Other assets	(73)	73
LIABILITIES AND SHAREHOLDER’S EQUITY
Deferred income taxes	37	(36)
Other liabilities	(225)	219
Retained earnings	115	$ (110)
Balances without Adoption [Member] | Accounting Standards Update 2014-09 [Member]
ASSETS
Other assets	2,087
LIABILITIES AND SHAREHOLDER’S EQUITY
Deferred income taxes	5,496
Other liabilities	4,229
Retained earnings	$ 12,485