Shareholders' Equity (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Class of Stock [Line Items]
Treasury Shares	24,034,053	23,567,979
Authorized stock repurchase program, amount	$ 262,000
Stock repurchased during period	398
Repurchased shares, amount	$ 69,255	$ 168,735	$ 62,550
Preferred stock, authorized (in shares)	1,000,000
Preferred stock, issued (in shares)	0
Treasury Stock
Class of Stock [Line Items]
Repurchased shares, amount	$ 69,255	$ 168,735	$ 62,550
Nonvoting Common Stock
Class of Stock [Line Items]
Common stock repurchased (in shares)	1,156,184	3,749,493	1,961,442