Inventories (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Inventories [Abstract]
Terms of precious metals consignment agreements, maximum	1 year
Fees under precious metals consignment agreements	$ 3.1	$ 2.1	$ 1.2
Fair value of precious metals on hand under consignment agreements	$ 66.2	$ 55.2