Debt - Senior Unsecured Notes (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Total Principal	$ 1,000,000
Long-term Debt, Total	1,026,111
Senior Unsecured Debt [Member]
Total Principal	510,000	$ 510,000
Unamortized debt issuance costs	(774)	(802)
Long-term Debt, Total	509,226	509,198
Senior Unsecured Debt [Member] | 2025 Senior Unsecured Notes [Member]
Total Principal	50,000	50,000
Senior Unsecured Debt [Member] | 2027 Senior Unsecured Notes [Member]
Total Principal	50,000	50,000
Senior Unsecured Debt [Member] | 2028 Senior Unsecured Notes [Member]
Total Principal	60,000	60,000
Senior Unsecured Debt [Member] | 2029 Senior Unsecured Notes [Member]
Total Principal	100,000	100,000
Senior Unsecured Debt [Member] | 2030 Senior Unsecured Notes [Member]
Total Principal	125,000	125,000
Senior Unsecured Debt [Member] | 2031 Senior Unsecured Notes [Member]
Total Principal	$ 125,000	$ 125,000