Significant Accounting Policies - Shares Used in Computation of Basic and Diluted Per Share Information (Details) - shares shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Accounting Policies [Abstract]
Weighted average number of shares outstanding for basic per share calculation (in shares)	31,225	31,104	31,188	31,060
Effect of dilutive potential shares:
Nonvested stock (in shares)	205	220	235	241
Adjusted weighted average shares for diluted per share calculation (in shares)	31,430	31,324	31,423	31,301
Anti-dilutive shares (in shares)	0	5	119	122