Stockholders' Equity (Narrative) (Details) - USD ($) shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 11, 2018
Stockholders' Equity Note [Abstract]
Dividends paid			$ 174,700,000	$ 179,200,000
Stock repurchase program, authorized amount					$ 300,000,000.0
Shares repurchased (in shares)			4.0
Shares repurchased, value	$ 2,600,000	$ 142,200,000	$ 92,700,000	$ 384,200,000