Significant Accounting Policies - Deferred Financing Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Debt Issuance Costs [Roll Forward]
Balance at beginning of period	$ 25,621	$ 22,712
Capitalized	23,202	12,731
Amortized	(9,031)	(9,822)	$ (9,074)
Balance at end of period	$ 39,792	$ 25,621	$ 22,712