Debt - Convertible Debt (Details) - Convertible Debt [Member]	12 Months Ended
	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Debt Instrument [Line Items]
Outstanding Balance	$ 321,802,000	$ 402,500,000
Unamortized discount	1,855,000	$ 3,909,000
2020 Convertible Notes [Member]
Debt Instrument [Line Items]
Repurchased debt	$ 80,700,000
Interest Rate	3.75%
Outstanding Balance	$ 321,800,000
Carrying value conversion options in additional paid-in capital	12,300,000
Unamortized discount	$ 1,900,000
Remaining amortization period	1 year
Conversion Rate	0.0667249
Amount of General Partner OP Units per principal amount	$ 1,000