Stockholders' Deficit (Summary of Common Stock Repurchase) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2023	Sep. 30, 2022
Equity [Abstract]
Treasury Stock Shares Repurchased	$ 1.1	$ 3.1
Treasury Stock Shares Repurchased for Tax Withholding and Other	$ 0.0	$ 0.1
Common stock repurchase, share	1.1	3.2
Treasury stock shares repurchased, average cost per share	$ 208.41	$ 211.10
Treasury stock, value, repurchased for tax withholding	$ 2.6	$ 16.0
Total repurchases for tax withholdings and other, average cost per share	$ 206.42	$ 212.08
Average stock price	$ 208.39	$ 211.13
Aggregate cost of share	$ 219.9	$ 659.8
Payments for Repurchase of Common Stock	$ 222.4	$ 675.8	$ 834.0