Fair Value Measurements (Fair Value of Long-term Borrowings Outstanding) (Details) - USD ($) $ in Thousands		12 Months Ended
	Nov. 14, 2019	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Debt instrument term		15 years
Fixed rate long-term notes payable
Debt Instrument [Line Items]
Debt instrument term	15 years
Carrying Amount
Debt Instrument [Line Items]
Fair value of long-term borrowings		$ 326,521	$ 288,942
Carrying Amount | Fixed rate long-term notes payable
Debt Instrument [Line Items]
Fair value of long-term borrowings		300,446	261,618
Carrying Amount | Debenture bonds
Debt Instrument [Line Items]
Fair value of long-term borrowings		26,075	27,324
Fair Value | Level 2
Debt Instrument [Line Items]
Fair value of long-term borrowings		333,756	282,601
Fair Value | Level 2 | Fixed rate long-term notes payable
Debt Instrument [Line Items]
Fair value of long-term borrowings		307,904	256,447
Fair Value | Level 2 | Debenture bonds
Debt Instrument [Line Items]
Fair value of long-term borrowings		$ 25,852	$ 26,154