Equity (Share Activity) (Narrative) (Details) - USD ($) shares in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Mar. 19, 2020	Dec. 21, 2018	Sep. 11, 2018	Mar. 29, 2018	Feb. 25, 2016
Equity, Treasury Stock [Line Items]
Treasury stock acquired (in shares)	3.6		7.2
Treasury stock acquired, value	$ 120,228,000	$ 602,000	$ 319,001,000
Stock repurchase program, remaining authorized repurchase amount	$ 158,600,000
September 2018 Share Repurchase Program [Member]
Equity, Treasury Stock [Line Items]
Treasury stock acquired (in shares)	0.6		2.9
Treasury stock acquired, value	$ 28,800,000		$ 120,600,000
Share repurchase program, amount authorized, value						$ 150,000,000
December 2018 Share Repurchase Program [Member]
Equity, Treasury Stock [Line Items]
Treasury stock acquired (in shares)	3.0
Treasury stock acquired, value	$ 91,400,000
Share repurchase program, amount authorized, value					$ 100,000,000
Stock repurchase program, remaining authorized repurchase amount	8,600,000
2016 Share Repurchase Program [Member]
Equity, Treasury Stock [Line Items]
Treasury stock acquired (in shares)			2.0
Treasury stock acquired, value			$ 98,400,000
Share repurchase program, amount authorized, value								$ 100,000,000
March 2018 Share Repurchase Program [Member]
Equity, Treasury Stock [Line Items]
Treasury stock acquired (in shares)			2.3
Treasury stock acquired, value			$ 100,000,000
Share repurchase program, amount authorized, value							$ 100,000,000
March 2020 Share Repurchase Program [Member]
Equity, Treasury Stock [Line Items]
Share repurchase program, amount authorized, value				$ 150,000,000
Stock repurchase program, remaining authorized repurchase amount	$ 150,000,000