Earnings per Share Repurchase of Common Stock (Details) - USD ($)	3 Months Ended					9 Months Ended
	Sep. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2015
Stock Repurchased and Retired During Period, Value	$ 4,480,000	$ 31,570,000	$ 5,670,000	$ 14,750,000	$ 670,000
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	188,028		196,128			1,441,678	723,528
Stock Repurchased and Retired During Period, Value	$ 4,500,000		$ 5,700,000			$ 36,000,000.0	$ 21,100,000
Stock Repurchase Program, Remaining Authorized Repurchase Amount	$ 165,100,000					$ 165,100,000