Earnings per Share Repurchase of Common Stock (Details) - USD ($)	3 Months Ended				6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2015
Stock Repurchased and Retired During Period, Value	$ 11,570,000	$ 2,640,000		$ 31,570,000
10b5-1 share repurchase program [Member]
Stock Repurchase Program, Authorized Amount	$ 250,000,000				$ 250,000,000		$ 50,000,000
Stock Repurchased and Retired During Period, Shares	358,047		0		440,218	1,253,650
Stock Repurchased and Retired During Period, Value	$ 11,600,000				$ 14,200,000	$ 31,600,000
Stock Repurchase Program, Remaining Authorized Repurchase Amount	$ 147,500,000				$ 147,500,000