Summary of Significant Accounting Policies and Procedures and Recent Accounting Pronouncements - Revenue Recognition and Accounts Receivable (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue Recognition and Accounts Receivable
Other revenue	$ 6.3	$ 3.5	$ 2.7