Derivative Instruments and Hedging Activities - Schedule of Estimated Gross Fair Values of Derivative Instruments and Their Classification on Consolidated Balance Sheet (Details) - Cash Flow Hedges - Derivatives Designated as Hedging Instruments - Interest Rate Swap Agreements - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Liabilities:
Derivative liabilities	$ 40,583	$ 16,238
Current Portion of Long-term Liabilities
Liabilities:
Current portion of long-term liabilities	15,140	4,947
Other Long-term Liabilities
Liabilities:
Other long-term liabilities	$ 25,443	$ 11,291