Commitments and Contingencies - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Loss Contingencies [Line Items]
Loss Contingency, Inestimable Loss	0
Outstanding performance and surety bonds	$ 341.4
Non-refundable deposits	143.7
Remaining purchase price of land	744.2
Project construction commitment
Loss Contingencies [Line Items]
Other commitment	291.3
Accrued Expenses
Loss Contingencies [Line Items]
Lease liability	$ 14.2	$ 14.6