Shareholders' Equity Cash Dividends Declared Per Common Share (Details) - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Equity [Abstract]
Cash dividends declared and paid per common share (in dollars per share)	$ 0.58	$ 0.55	$ 1.74	$ 1.65