Consolidated 50% Owned Subsidiaries Consolidated 50% Owned Subsidiaries - Statement of Operations (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Variable Interest Entity [Line Items]
Operating income	$ 33,046	$ 11,184	$ 45,149	$ 15,904
Net income	18,210	7,828	21,325	9,643
Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Revenues	54,364	59,664	98,726	102,078
Operating income	1,049	2,004	1,204	2,281
Net income	$ 1,051	$ 2,009	$ 1,209	$ 2,291