Shareholders' Equity (Schedule of Dividend Activity) (Details) - $ / shares	3 Months Ended															9 Months Ended	12 Months Ended
	Dec. 31, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Sep. 30, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Stockholders' Equity Note [Abstract]
Cash dividends paid per common share for all classes of common shares (in dollars per share)	$ 0.15	$ 0.30	$ 0.30	$ 0.30	$ 0.30	$ 0.30	$ 0.30	$ 0.30	$ 0.30	$ 0.30	$ 0.30					$ 0.30	$ 1.05	$ 1.20	$ 1.20
Dividends declared (in dollars per share)				$ 0.3	$ 0.3	$ 0.3	$ 0.15	$ 0.3	$ 0.3	$ 0.3	$ 0.3	$ 0.3	$ 0.3	$ 0.3	$ 0.3		$ 1.05	$ 1.2	$ 1.2