Credit Facilities	12 Months Ended
	Dec. 31, 2021
Notes To Financial Statements [Abstract]
Credit Facilities	Credit FacilityOn July 21, 2020 we entered into a credit facility for a $300.0 million unsecured revolving line of credit, with a $50.0 million letter of credit sublimit, and a maturity date of July 21, 2023 (“2020 Credit Facility”). The 2020 Credit Facility requires us to comply with specific financial conditions and performance requirements. Loans under the 2020 Credit Facility bear interest, at our option, at either a rate based on the reserve adjusted LIBOR for the applicable interest period or a base rate, in each case plus a margin. The base rate is the highest of the credit facility’s publicly announced prime rate, the federal funds rate plus 0.50% and one-month LIBOR plus 1.0%. The margin ranges from 1.50% to 2.25% for LIBOR loans and 0.50% to 1.25% for base rate loans. The 2020 Credit Facility allows for an alternative rate to be identified if LIBOR is no longer available. Interest on the loans is payable quarterly in arrears with respect to base rate loans and at the end of an interest period (and at three month intervals if the interest period exceeds three months) in the case of LIBOR loans. The outstanding principal, together with accrued and unpaid interest, is due on the maturity date. As of December 31, 2021, we had no outstanding borrowings under the 2020 Credit Facility and were in compliance with the conditions and performance requirements.