Fair Value Measurements (Summary of Carrying Value and Fair Value of the Company's Financial Instruments Disclosed but not Carried at Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notes payable	$ 372,532	$ 372,133
Borrowings [Member] | Unsecured Debt [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notes payable	372,532	372,133
Notes payable, fair value	415,253	394,279
Borrowings [Member] | Unsecured Debt [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notes payable, fair value	0	0
Borrowings [Member] | Unsecured Debt [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notes payable, fair value	415,253	394,279
Borrowings [Member] | Unsecured Debt [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notes payable, fair value	$ 0	$ 0