Fair Value Measurements Fair Value Measurements (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	$ 579,096	$ 579,105
US Government Securities, at Carrying Value	6,856	5,782
Municipal bonds	25,754	26,009
Total	611,706	610,896
US Treasury Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	6,874	5,783
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	18	1
Debt Securities, Available-for-sale	6,856	5,782
Municipal Bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	25,837	26,017
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	83	8
Debt Securities, Available-for-sale	25,754	26,009
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	579,096	579,105
US Government Securities, at Carrying Value	6,856	5,782
Municipal bonds	0	0
Total	585,952	584,887
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	0	0
US Government Securities, at Carrying Value	0	0
Municipal bonds	25,754	26,009
Total	$ 25,754	$ 26,009