Fair Value Disclosures - Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Interest Rate Swap
Liabilities:
Interest rate swaps	$ (12,400)
Recurring | SERP
Assets:
SERP	2,126	$ 1,792
Recurring | Interest Rate Swap
Assets:
Interest rate swaps	0	5,549
Liabilities:
Interest rate swaps	(12,372)	(3,726)
Recurring | Level 1 | SERP
Assets:
SERP	0	0
Recurring | Level 1 | Interest Rate Swap
Assets:
Interest rate swaps	0	0
Liabilities:
Interest rate swaps	0	0
Recurring | Level 2 | SERP
Assets:
SERP	2,126	1,792
Recurring | Level 2 | Interest Rate Swap
Assets:
Interest rate swaps	0	5,549
Liabilities:
Interest rate swaps	(12,372)	(3,726)
Recurring | Level 3 | SERP
Assets:
SERP	0	0
Recurring | Level 3 | Interest Rate Swap
Assets:
Interest rate swaps	0	0
Liabilities:
Interest rate swaps	$ 0	$ 0