Capital Stock (Tables)

6 Months Ended

Jun. 30, 2021

Banking Regulation, Total Capital [Abstract]

Summary of Cash Dividend Activity

A summary of our cash dividend activity for the six months ended June 30, 2021 and 2020 is as follows: 

Declaration Date	Record Date	Payment Date	Cash Dividend per Share	Total
Six Months Ended June 30, 2021
January 26, 2021	March 10, 2021	March 25, 2021	$1.13	$	277
April 20, 2021	June 10, 2021	June 25, 2021	$1.13	$	278
Six Months Ended June 30, 2020
January 28, 2020	March 16, 2020	March 27, 2020	$0.95	$	240
April 28, 2020	June 10, 2020	June 25, 2020	$0.95	$	242

Summary of Share Repurchases

A summary of common stock repurchases for the six months ended June 30, 2021 and 2020 is as follows:

	Six Months Ended June 30
	2021		2020
Shares repurchased	2.7		2.1
Average price per share	$	346.47	$	273.72
Aggregate cost	$	927	$	584
Authorization remaining at the end of the period	$	5,165	$	3,208

Summary of Stock Option Activity

A summary of stock option activity for the six months ended June 30, 2021 is as follows:

	Number of Shares	Weighted- Average Option Price per Share		Weighted- Average Remaining Contractual Life (Years)	Aggregate Intrinsic Value
Outstanding at January 1, 2021	3.1	$	230.00
Granted	0.7	312.33
Exercised	(0.6)	193.55
Forfeited or expired	(0.1)	286.70
Outstanding at June 30, 2021	3.1	253.91		7.23	$	402
Exercisable at June 30, 2021	1.6	215.56		5.94	$	270

Summary of Nonvested Restricted Stock Activity Including Restricted Stock Units

A summary of the nonvested restricted stock activity, including restricted stock units, for the six months ended June 30, 2021 is as follows:

	Restricted Stock Shares and Units	Weighted- Average Grant Date Fair Value per Share
Nonvested at January 1, 2021	1.3	$	272.51
Granted	0.9	312.50
Vested	(0.8)	244.24
Forfeited	(0.1)	287.67
Nonvested at June 30, 2021	1.3	295.57

Summary of Weighted-Average Assumptions Used to Estimate the Fair Value of Options Granted During the Periods

The following weighted-average assumptions were used to estimate the fair values of options granted during the six months ended June 30, 2021 and 2020:

	Six Months Ended June 30
	2021		2020
Risk-free interest rate	1.44	%	1.30	%
Volatility factor	30.00	%	26.00	%
Quarterly dividend yield	0.360	%	0.350	%
Weighted-average expected life (years)	5.50		4.30

Schedule of Weighted-Average Fair Values Determined for the Periods

The following weighted-average fair values per option or share were determined for the six months ended June 30, 2021 and 2020: 

	Six Months Ended June 30
	2021		2020
Options granted during the period	$	79.22	$	54.04
Restricted stock awards granted during the period	312.50		272.14