Summary of Significant Accounting Policies (Share Repurchases) (Details) - Convertible Notes - 2036 Senior Convertible Notes Repurchases - USD ($)		3 Months Ended
	Jun. 02, 2016	Mar. 31, 2020	Mar. 31, 2019
Equity, Class of Treasury Stock [Line Items]
Convertible Notes Repurchases, Principal amount		$ 11,008,000	$ 11,008,000
Convertible Notes Repurchases	$ 147,118,000	$ 25,949,000	0
January 2019 Program
Equity, Class of Treasury Stock [Line Items]
Convertible Notes Repurchases			$ 25,949,000