Summary of Significant Accounting Policies - Government Grant Income (Details) - Government Assistance, CARES Act - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Unusual or Infrequent Item, or Both [Line Items]
Government grant income received	$ 1,099	$ 14,884	$ 6,067	$ 14,884
Government grant income recorded in other income (expense), net
Unusual or Infrequent Item, or Both [Line Items]
Government grant income received	87	11,871	1,397	11,871
Government grant income recorded in equity income (loss) from unconsolidated joint ventures
Unusual or Infrequent Item, or Both [Line Items]
Government grant income received	584	804	1,010	804
Government grant income recorded in income (loss) from discontinued operations
Unusual or Infrequent Item, or Both [Line Items]
Government grant income received	$ 428	$ 2,209	$ 3,660	$ 2,209