Common, Preferred and Treasury Stock (Accelerated Share Repurchase Transactions) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accelerated Share Repurchases [Line Items]
Shares acquired for treasury	$ 1,763	$ 1,453	$ 1,605
December 19. 2017 ASR
Accelerated Share Repurchases [Line Items]
Settlement date	Mar. 19, 2018
Redemption date	Dec. 19, 2017
December 19. 2017 ASR | February 2018 Repurchase Program
Accelerated Share Repurchases [Line Items]
Shares acquired for treasury	$ 273
Shares repurchased on repurchase date	7,727,273
Shares received from forward contract settlement	824,367
Total shares repurchased	8,551,640
February 12, 2018 ASR
Accelerated Share Repurchases [Line Items]
Settlement date	Mar. 26, 2018
Redemption date	Feb. 12, 2018
February 12, 2018 ASR | February 2018 Repurchase Program
Accelerated Share Repurchases [Line Items]
Shares acquired for treasury	$ 318
Shares repurchased on repurchase date	8,691,318
Shares received from forward contract settlement	1,015,731
Total shares repurchased	9,707,049
May 25, 2018 ASR
Accelerated Share Repurchases [Line Items]
Settlement date	Jun. 15, 2018
Redemption date	May 25, 2018
May 25, 2018 ASR | February 2018 Repurchase Program
Accelerated Share Repurchases [Line Items]
Shares acquired for treasury	$ 235
Shares repurchased on repurchase date	6,402,244
Shares received from forward contract settlement	1,172,122
Total shares repurchased	7,574,366
July 20, 2018 through August 2, 2018 Open Market Repurchase
Accelerated Share Repurchases [Line Items]
Settlement date	Aug. 06, 2018
July 20, 2018 through August 2, 2018 Open Market Repurchase | March 2018 Repurchase Program
Accelerated Share Repurchases [Line Items]
Shares acquired for treasury		$ 500
Shares repurchased on repurchase date		16,945,020
Settlement date		Jul. 24, 2018
October 24, 2018 through November 9, 2018 Open Market Repurchase
Accelerated Share Repurchases [Line Items]
Settlement date	Nov. 14, 2018
October 24, 2018 through November 9, 2018 Open Market Repurchase | March 2018 Repurchase Program
Accelerated Share Repurchases [Line Items]
Shares acquired for treasury		$ 400
Shares repurchased on repurchase date		14,916,332
March 27, 2019 ASR
Accelerated Share Repurchases [Line Items]
Settlement date	Jun. 28, 2019
Redemption date	Mar. 27, 2019
March 27, 2019 ASR | February 2018 Repurchase Program
Accelerated Share Repurchases [Line Items]
Shares acquired for treasury	$ 913
Shares repurchased on repurchase date	31,779,280
Shares received from forward contract settlement	2,026,584
Total shares repurchased	33,805,864
April 29, 2019 ASR
Accelerated Share Repurchases [Line Items]
Redemption date	Apr. 29, 2019
April 29, 2019 ASR | Maximum [Member]
Accelerated Share Repurchases [Line Items]
Settlement date	May 24, 2019
April 29, 2019 ASR | Minimum [Member]
Accelerated Share Repurchases [Line Items]
Settlement date	May 23, 2019
April 29, 2019 ASR | February 2018 Repurchase Program
Accelerated Share Repurchases [Line Items]
Shares acquired for treasury	$ 200
Shares repurchased on repurchase date	6,015,570
Shares received from forward contract settlement	1,217,805
Total shares repurchased	7,233,375
August 7, 2019 ASR
Accelerated Share Repurchases [Line Items]
Settlement date	Aug. 16, 2019
Redemption date	Aug. 07, 2019
August 7, 2019 ASR | February 2018 Repurchase Program
Accelerated Share Repurchases [Line Items]
Shares acquired for treasury	$ 100
Shares repurchased on repurchase date	3,150,482
Shares received from forward contract settlement	694,238
Total shares repurchased	3,844,720
August 9, 2019 ASR
Accelerated Share Repurchases [Line Items]
Settlement date	Aug. 28, 2019
Redemption date	Aug. 09, 2019
August 9, 2019 ASR | February 2018 Repurchase Program
Accelerated Share Repurchases [Line Items]
Shares acquired for treasury	$ 200
Shares repurchased on repurchase date	6,405,426
Shares received from forward contract settlement	1,475,487
Total shares repurchased	7,880,913
October 25, 2019 ASR
Accelerated Share Repurchases [Line Items]
Settlement date	Dec. 17, 2019
Redemption date	Oct. 25, 2019
October 25, 2019 ASR | February 2018 Repurchase Program
Accelerated Share Repurchases [Line Items]
Shares acquired for treasury	$ 300
Shares repurchased on repurchase date	9,020,163
Shares received from forward contract settlement	1,149,121
Total shares repurchased	10,169,284
July 29, 2019 through July 30, 2019 Open Market Repurchase | March 2018 Repurchase Program
Accelerated Share Repurchases [Line Items]
Shares acquired for treasury	$ 50
Shares repurchased on repurchase date	1,667,735
Settlement date	Jul. 31, 2019