Revenue Recognition - Graduation Fund (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Graduation Fund [Roll Forward]
Balance at beginning of period	$ 52,024	$ 53,314
Revenue deferred	8,774	11,435
Benefit redeemed	(10,656)	(11,185)
Balance at end of period	$ 50,142	$ 53,564