Shareholders' Equity (Schedule of Stock by Class) (Details) - $ / shares	Feb. 16, 2018	Dec. 31, 2019	May 20, 2019	May 19, 2019	Dec. 31, 2018	Dec. 31, 2017
Class of Stock [Line Items]
Shares, Issued	1,006,061
Treasury Stock (shares)		1,600,000			2,700,000
Common Class A
Class of Stock [Line Items]
Common stock, par value (in dollars per share)		$ 0.025			$ 0.025
Authorized Shares		105,000,000.0	105,000,000.0	80,000,000.0	105,000,000
Common Stock Outstanding (shares)		39,200,000			38,100,000	38,200,000
Treasury Stock (shares)		1,100,000			2,200,000	1,800,000
Total Issued Shares		40,300,000			40,300,000	40,000,000.0
Common Class B
Class of Stock [Line Items]
Common stock, par value (in dollars per share)		$ 0.025			$ 0.025
Authorized Shares		80,000,000.0			80,000,000
Common Stock Outstanding (shares)		13,500,000			13,500,000	13,800,000
Treasury Stock (shares)		0			0	0
Total Issued Shares		13,500,000			13,500,000	13,800,000
Common Class C
Class of Stock [Line Items]
Common stock, par value (in dollars per share)		$ 0.025			$ 0.025
Authorized Shares		20,000,000.0			20,000,000
Common Stock Outstanding (shares)		0			0	0
Treasury Stock (shares)		500,000			500,000	500,000
Total Issued Shares		500,000			500,000	500,000