Stockholders' Equity - Dividends (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Accumulated Other Comprehensive Loss
Dividends declared per common share (in dollars per share)	$ 0.90	$ 0.90	$ 0.85	$ 1.80	$ 1.70
Aggregated dividend paid	$ 46.3	$ 46.3
Dividend payable date declared	Jun. 18, 2019			Feb. 26, 2019
Common stock Dividend Payable Date	Jul. 15, 2019	Apr. 15, 2019
Dividend payable date of record	Jun. 28, 2019	Mar. 29, 2019