Debt - Cash Paid for Interest and Capitalized Interest (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Debt Disclosure [Abstract]
Cash paid for interest	$ 59.5	$ 39.9	$ 22.1
Capitalized interest expense	$ 6.0	$ 4.2	$ 3.0