Leases (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Leases [Abstract]
Operating Lease, Right-of-Use Asset	$ 19.2
Operating lease expense	12.0	$ 12.4	$ 19.2
Royalty expense	149.5	$ 166.1	$ 167.4
Surety bonds outstanding	$ 29.5