Derivative Instruments and Hedging Activities Derivative Instruments and Hedging Activities - Interest Rate Swap Agreements (Details) - Interest Rate Swap Agreements - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Jul. 31, 2019
Derivative [Line Items]
Notional amount	$ 350,000,000		$ 350,000,000		$ 350,000,000	$ 350,000,000
Unrealized losses associated with cash flow hedges	898,000	$ 4,931,000	15,630,000	$ 7,605,000
Cumulative net losses in AOCI	24,404,000		24,404,000
Other Long-Term Liabilities
Derivative [Line Items]
Derivative liability	$ 24,404,000		$ 24,404,000		$ 8,774,000