Stockholders' Equity - Dividends (Details) - USD ($) $ / shares in Units, $ in Millions									12 Months Ended
	Dec. 13, 2019	Nov. 06, 2019	Sep. 13, 2019	Jun. 14, 2019	Mar. 22, 2019	Aug. 06, 2018	May 07, 2018	Feb. 28, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Equity [Abstract]
Cash payment amount	$ 5.5		$ 5.1	$ 5.1	$ 5.1				$ 20.7	$ 18.9	$ 17.2
Dividends declared per share (in dollars per share)		$ 0.12				$ 0.11	$ 0.11	$ 0.11	$ 0.45	$ 0.41	$ 0.37