Financial Instruments - Derivatives and Hedging (Cash Flow Hedging Relationship) (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Change in unrealized loss on interest rate swaps	$ (3,180)	$ (12,306)	$ (27,011)	$ (19,250)
Amortization (accretion) of interest rate swaps to interest expense	2,345	(1,678)	2,298	(4,791)
Change in unrealized loss on interest rate swaps, net	$ (835)	$ (13,984)	$ (24,713)	$ (24,041)

Amount after tax of reclassification adjustment from accumulated other comprehensive income of accumulated gain (loss) realized from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's deferred hedging gain (loss).

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