Common Stock Stock Repurchase (Details) - USD ($) $ in Thousands		3 Months Ended			9 Months Ended		12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Mar. 31, 2020	Apr. 30, 2019
Equity, Class of Treasury Stock [Line Items]
Document Period End Date					Sep. 30, 2019
Stock Repurchase Program, Authorized Amount								$ 525,000	$ 200,000
Payments for Repurchase of Common Stock					$ 3,874	$ 4,700
Other Nonoperating Expense					2,818		$ 0
Stock Repurchase Program, Remaining Authorized Repurchase Amount			$ 45,700		$ 45,700
Subsequent Event [Member]
Equity, Class of Treasury Stock [Line Items]
Stock Repurchase Program Expiration Date	Dec. 31, 2020
Treasury Stock, Common [Member]
Equity, Class of Treasury Stock [Line Items]
Stock Repurchased During Period, Shares			(1,228,310)	(3,136,406)	(4,400,000)
Payments for Repurchase of Common Stock			$ (40,300)		$ (145,500)
Other Nonoperating Expense					2,800	$ 0
Treasury Stock, Common [Member] | Amount settled during period [Member]
Equity, Class of Treasury Stock [Line Items]
Payments for Repurchase of Common Stock					$ 142,700
Treasury Stock, Common [Member] | Subsequent Event [Member]
Equity, Class of Treasury Stock [Line Items]
Stock Repurchased During Period, Shares		(300,000)
Payments for Repurchase of Common Stock		$ 8,900