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Stockholders' Equity and Earnings Per Share (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Stockholders' Equity and Earnings Per Share [Line Items]
Stock repurchase program, amount authorized					$ 500.0
Repurchased by company (in shares)					4,471,682
Average price (in dollars per share)					$ 32.64
Total cost					$ 146.0
RSUs
Stockholders' Equity and Earnings Per Share [Line Items]
Weighted-average anti-dilutive shares (in shares)	2,000,000	124,000	6,000,000	123,000