Stockholders' Equity (Common Stock) (Details) - USD ($) $ / shares in Units, shares in Millions	1 Months Ended		12 Months Ended
	Mar. 31, 2019	Feb. 28, 2017	Feb. 02, 2019	Feb. 03, 2018	Jan. 28, 2017	Mar. 31, 2018	Feb. 28, 2018
Class of Stock [Line Items]
Stock repurchased program period		2 years
Stock repurchase program, approved amount		$ 1,750,000,000
Stock repurchase program, authorized increase						$ 200,000,000
Stock repurchase program, remaining amount						$ 1,075,000,000	$ 875,000,000
Shares repurchased (in shares)			12.5	13.5	11.6
Average repurchase price (in dollars per share)			$ 86.19	$ 64.87	$ 60.15
Common stock repurchased, value			$ 1,075,000,000	$ 875,000,000	$ 700,000,000
Subsequent Event
Class of Stock [Line Items]
Stock repurchased program period	2 years
Stock repurchase program, approved amount	$ 2,550,000,000.00