Stockholders' Equity - Additional Information (Detail) - USD ($)		3 Months Ended		9 Months Ended		12 Months Ended
	May 07, 2019	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Nov. 30, 2018	Feb. 28, 2018	Nov. 30, 2016	Jul. 31, 2012
Stockholders Equity Note [Line Items]
Cash dividends declared per common share (in dollars per share)		$ 0.22	$ 0.19	$ 0.63	$ 0.54
Stock repurchase program, authorized amount										$ 2,000,000,000.0
Stock repurchase program, additional authorized amount							$ 2,000,000,000.0	$ 1,500,000,000	$ 1,500,000,000
Share repurchases (in shares)				13,500,000	14,900,000
Stock Repurchase Program, Liability		$ 37,000,000		$ 37,000,000
Remaining value available under stock repurchase programs		1,100,000,000		$ 1,100,000,000
Purchases of treasury stock (in shares)				13,500,000	14,900,000
Purchases of treasury stock		$ 346,000,000	$ 247,000,000	$ 1,043,000,000	$ 1,028,000,000
ASR Agreement
Stockholders Equity Note [Line Items]
Stock repurchase program, authorized amount						$ 300,000,000
Share repurchases (in shares)	600,000					3,600,000
Purchases of treasury stock (in shares)	600,000					3,600,000