Summary of Significant Accounting Policies - Interest Cost Capitalized and Incurred (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Summary of Significant Accounting Policies
Interest incurred									$ 11,311	$ 2,292	$ 2,656
Interest capitalized										756	487
Interest expense	$ 2,943	$ 2,875	$ 2,907	$ 2,586	$ 575	$ 558	$ 57	$ 346	$ 11,311	$ 1,536	$ 2,169