Stockholders Equity Dividends table (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Class of Stock [Line Items]
Cash dividends per common share	$ 0.48	$ 0.46	$ 2.46	$ 2.42
Cash dividends per preferred share	0.0075	0.0075	$ 0.0150	$ 0.0150
Payment Of Special Cash Dividend			$ 37.0	$ 37.3
Regular quarterly cash dividend
Class of Stock [Line Items]
Cash dividends per common share	0.48	0.46	$ 0.96	$ 0.92
Special cash dividend
Class of Stock [Line Items]
Cash dividends per common share	$ 0	$ 0	$ 1.50	$ 1.50