Summary of Significant Accounting Policies - Reclassifications (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total operating expenses	$ 442,762	$ 436,236
Revision of Prior Period, Reclassification, Adjustment [Member] | General and Administrative Expense [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total operating expenses		(5,900)
Revision of Prior Period, Reclassification, Adjustment [Member] | Direct Operating Maintenance Supplies Costs [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total operating expenses		$ 5,900