Inventories (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Inventories [Abstract]
Terms of precious metals consignment agreements, maximum			1 year
Fees under precious metals consignment agreements	$ 0.6	$ 0.5	$ 2.3	$ 2.2
Fair value of precious metals on hand under consignment agreements	$ 87.5		$ 87.5		$ 66.2