Stockholders' Equity - Dividends (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended
	Feb. 14, 2018	Mar. 31, 2018	Mar. 31, 2017
Equity [Abstract]
Quarterly cash dividend (in dollars per share)	$ 0.16	$ 0.16	$ 0.16
Amount of quarterly cash dividend declared	$ 26.5