Shareholders' Equity (Details) - shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Treasury stock	14,592,888	14,592,888
Class A
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued, beginning balance	66,033,509	65,891,930	65,067,132
Share issuances	5,651,177	0	0
Issuance pursuant to benefit plans	19,919	34,760	292,514
Restricted stock forfeited and withheld for taxes	(51,049)	(126,682)	0
Stock options exercised	21,823	233,501	532,284
Shares issued, ending balance	71,675,379	66,033,509	65,891,930
Treasury stock	14,592,888		11,655,938
Treasury stock	57,082,491	51,440,621	54,235,992
Class B
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued, beginning balance	0
Share issuances	23,793,669
Issuance pursuant to benefit plans	0
Restricted stock forfeited and withheld for taxes	0
Stock options exercised	0
Shares issued, ending balance	23,793,669	0
Treasury stock			0
Treasury stock	23,793,669