Equity (Share Activity) (Narrative) (Details) - USD ($)	3 Months Ended			6 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Mar. 31, 2018	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 21, 2018	Sep. 11, 2018	Dec. 31, 2016
Equity, Treasury Stock [Line Items]
Treasury stock acquired (in shares)	0	1,600,000	2,000,000.0	2,300,000		4,300,000
Treasury stock acquired, value		$ 70,137,000	$ 98,400,000		$ 602,000	$ 198,448,000
Share repurchase program, amount available for future share repurchases, value	$ 128,800,000				128,800,000
September 2018 Share Repurchase Program [Member]
Equity, Treasury Stock [Line Items]
Share repurchase program, amount authorized, value								$ 150,000,000
Share repurchase program, amount available for future share repurchases, value	28,800,000				28,800,000
2016 Share Repurchase Program [Member]
Equity, Treasury Stock [Line Items]
Share repurchase program, amount authorized, value									$ 100,000,000
March 2018 Share Repurchase Program [Member]
Equity, Treasury Stock [Line Items]
Share repurchase program, amount authorized, value			$ 100,000,000
December 2018 Share Repurchase Program [Member]
Equity, Treasury Stock [Line Items]
Share repurchase program, amount authorized, value							$ 100,000,000
Share repurchase program, amount available for future share repurchases, value	$ 100,000,000				$ 100,000,000