Fair Value Measurements - Assets and Liabilities at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Assets:
Value	$ 226,138	$ 221,894
Put Option
Assets:
Value	2,995	7,017
Life Insurance Policy
Assets:
Value	761,560	791,911
Level 1 | Put Option
Assets:
Value	2,995	7,017
Level 1 | Life Insurance Policy
Assets:
Value	0	0
Level 2 | Put Option
Assets:
Value	0	0
Level 2 | Life Insurance Policy
Assets:
Value	0	0
Level 3 | Put Option
Assets:
Value	0	0
Level 3 | Life Insurance Policy
Assets:
Value	$ 761,560	$ 791,911