Fair Value Measurements - Carrying Amount, Estimated Fair Values and Categorization Under the Fair Value Hierarchy of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Carrying Amount
Assets:
Cash and cash equivalents	$ 64,025	$ 108,966
Liabilities:
Fixed-rate long-term debt	585,027	585,824
Variable-rate long-term debt	494,299	599,221
Fair Value | Level 1
Assets:
Cash and cash equivalents	64,025	108,966
Liabilities:
Fixed-rate long-term debt	0	0
Variable-rate long-term debt	0	0
Fair Value | Level 2
Assets:
Cash and cash equivalents	0	0
Liabilities:
Fixed-rate long-term debt	465,449	541,267
Variable-rate long-term debt	498,875	602,652
Interest rate swaps | Carrying Amount
Assets:
Derivative asset	0	2,131
Liabilities:
Derivative liability	639
Interest rate swaps | Fair Value | Level 1
Assets:
Derivative asset	0	0
Interest rate swaps | Fair Value | Level 2
Assets:
Derivative asset	0	2,131
Liabilities:
Derivative liability	639
Foreign exchange forward contracts | Carrying Amount
Assets:
Derivative asset	5,108	7
Liabilities:
Derivative liability	1,115	19,873
Foreign exchange forward contracts | Fair Value | Level 1
Assets:
Derivative asset	0	0
Liabilities:
Derivative liability	0	0
Foreign exchange forward contracts | Fair Value | Level 2
Assets:
Derivative asset	5,108	7
Liabilities:
Derivative liability	$ 1,115	$ 19,873