Inventories (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Inventories [Abstract]
Terms of precious metals consignment agreements, maximum	1 year
Fees under precious metals consignment agreements	$ 2.9	$ 3.1	$ 2.1
Fair value of precious metals on hand under consignment agreements	$ 87.2	$ 66.2