Summary of Significant Accounting Policies - Fair Value Measurements (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Estimated fair value of long-term debt	$ 831,800	$ 755,000
Long-term debt, gross	842,000	755,000
Interest Rate Swap Agreements | Interest rate swap liability, current portion
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swaps	9,225	3,464
Interest Rate Swap Agreements | Interest rate swap liability, current portion | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swaps	9,225	3,464
Interest Rate Swap Agreements | Other long-term liabilities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swaps	23,685	10,550
Interest Rate Swap Agreements | Other long-term liabilities | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swaps	$ 23,685	$ 10,550