Shareholders' Equity (Schedule of Stock by Class) (Details)	Mar. 31, 2021 vote $ / shares shares	Dec. 31, 2020 $ / shares shares
Common Class A
Class of Stock [Line Items]
Common stock, par value (in dollars per share) | $ / shares	$ 0.025	$ 0.025
Authorized Shares	105,000,000.0	105,000,000.0
Outstanding	41,200,000	40,200,000
Treasury	500,000	200,000
Total Issued Shares	41,700,000	40,400,000
Number of votes | vote	1
Common Class B
Class of Stock [Line Items]
Common stock, par value (in dollars per share) | $ / shares	$ 0.025	$ 0.025
Authorized Shares	80,000,000.0	80,000,000.0
Outstanding	13,500,000	13,500,000
Treasury	0	0
Total Issued Shares	13,500,000	13,500,000
Number of votes | vote	10
Common Class C
Class of Stock [Line Items]
Common stock, par value (in dollars per share) | $ / shares	$ 0.025	$ 0.025
Authorized Shares	20,000,000.0	20,000,000.0
Outstanding	0	0
Treasury	500,000	500,000
Total Issued Shares	500,000	500,000
Number of votes | vote	10