Related-Party Transactions - Receivable and Payable Balance with Affiliates (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018
Receivable and Payable Balances with Affiliates
Receivable balances with affiliates	$ 716	$ 42	$ 206		$ 0
Increase to related party payables	1,740	$ 10,207	$ 11,671	$ 13,812	15,363	$ 15,792	$ 17,023	$ 14,172
HOV Services, Ltd
Receivable and Payable Balances with Affiliates
Receivable balances with affiliates	601
Increase to related party payables					405
Rule 14, LLC
Receivable and Payable Balances with Affiliates
Increase to related party payables	250				127
HGM
Receivable and Payable Balances with Affiliates
Receivable balances with affiliates	115
Increase to related party payables					6,998
Apollo
Receivable and Payable Balances with Affiliates
Increase to related party payables	202				205
Oakana Holdings Inc
Receivable and Payable Balances with Affiliates
Increase to related party payables	1
Ex-Sigma
Receivable and Payable Balances with Affiliates
Increase to related party payables	$ 1,287				$ 7,628