Common Stock Issued and Outstanding - Activity in the Number of Common Stock Issued and Outstanding (Details) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning of year	173,058,829	172,572,873	172,202,177
Stock options exercised	12,345	21,200	0
Restricted stock awards	561,729	464,756	368,132
Employee stock purchase and thrift plans	0	0	2,564
Treasury shares purchased	(20,697,542)	0	0
End of year	152,935,361	173,058,829	172,572,873