Stockholders' Equity Sale of Stock (Details) - USD ($) $ / shares in Units, $ in Millions	Apr. 03, 2018	Dec. 31, 2019	Dec. 31, 2018
Subsidiary, Sale of Stock [Line Items]
Common stock, par value (in dollars per share)		$ 0.01	$ 0.01
Equity Offering
Subsidiary, Sale of Stock [Line Items]
Newly issued shares of common stock in registered public offering (shares)	5,300,000
Common stock, par value (in dollars per share)	$ 0.01
Price per share (usd per share)	$ 175
Proceeds	$ 915.2
Underwriting discounts	11.7
Offering expenses	$ 0.6