Consolidated Statements of Shareholders' Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash dividends declared
Common stock, dividend per share	$ 1.48	$ 1.34	$ 1.22
Series B Preferred Stock [Member]
Cash dividends declared
Preferred stock, dividend per share	52	52	52
Series C Preferred Stock [Member]
Cash dividends declared
Preferred stock, dividend per share	$ 49	$ 49	$ 49