Fair Value of Financial Instruments - Fair Value of Long-Term Debt (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Total long-term debt, excluding debt issuance costs	$ 2,056,328	$ 3,588,157
Total long-term debt, fair value, excluding debt issuance costs	$ 2,259,180	$ 3,783,225