Significant Accounting Policies (Details Textual) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Effective Income Tax Rate Reconciliation, Percent	29.80%	28.20%	17.90%
Effective Income Tax Rate Reconciliation, Tax Cuts and Jobs Act, Amount	$ 0.0	$ 0.0	$ 16.5
Interest Expense, Deposits	1.5	3.8	5.7
Interest expense net of interest income on bank deposits	$ 190.3	180.5	$ 162.9
Accounting Standards Update 2016-02
Deferred Tax Assets, Deferred Gain on Sale Leaseback Transaction		$ 4.0