- Changes in Outstanding Common Stock (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Changes in Common Stock [Roll Forward]
Outstanding, beginning of year (in shares)	106,363	104,572	99,843
Shares issued for exercise of options (in shares)	281	603	416
Shares issued for time vested restricted stock (net of forfeitures) (in shares)	53	1,188	952
Shares issued for acquisition (in shares)	0	0	3,361
Outstanding, end of year (in shares)	106,697	106,363	104,572