Earnings per Share Purchase of Common Stock (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Stock Repurchased and Retired During Period, Value	$ 39,420,000	$ 36,740,000	$ 12,140,000
10b5-1 share repurchase program [Member]
Stock Repurchase Program, Authorized Amount	$ 250,000,000		$ 50,000,000
Stock Repurchased and Retired During Period, Shares	1,582,049	1,230,050	442,632
Stock Repurchased and Retired During Period, Value	$ 39,400,000	$ 36,700,000	$ 12,100,000
Stock Repurchase Program, Remaining Authorized Repurchase Amount	$ 161,700,000