Debt - Cash Pooling (Details) $ in Thousands	3 Months Ended
	Sep. 30, 2021 USD ($) cash_pool	Dec. 31, 2020 USD ($)
JP Morgan Chase Bank
Debt Instrument [Line Items]
Number of cash pools | cash_pool	2
Bank Mendes Gans
Debt Instrument [Line Items]
Number of cash pools | cash_pool	2
QRS Cash Pool | JP Morgan Chase Bank
Debt Instrument [Line Items]
Cash pool borrowings	$ 12,000
Number of cash pools | cash_pool	1
GROSS CASH POSITION	$ 4,200	$ 0
OUTSTANDING DEBIT BALANCES	(2,300)	0
NET CASH POSITION	$ 1,900	0
QRS Cash Pool | Bank Mendes Gans
Debt Instrument [Line Items]
Number of cash pools | cash_pool	1
GROSS CASH POSITION	$ 566,100	448,700
OUTSTANDING DEBIT BALANCES	(562,400)	(447,400)
NET CASH POSITION	3,700	1,300
TRS Cash Pool | JP Morgan Chase Bank
Debt Instrument [Line Items]
Cash pool borrowings	$ 10,000
Number of cash pools | cash_pool	1
GROSS CASH POSITION	$ 5,200	0
OUTSTANDING DEBIT BALANCES	(4,700)	0
NET CASH POSITION	$ 500	0
TRS Cash Pool | Bank Mendes Gans
Debt Instrument [Line Items]
Number of cash pools | cash_pool	1
GROSS CASH POSITION	$ 579,300	555,500
OUTSTANDING DEBIT BALANCES	(578,300)	(553,500)
NET CASH POSITION	$ 1,000	$ 2,000