Derivative Instruments and Hedging Activities - Effective Portion of Gains (Losses) on Interest Rate Swap Agreements (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Derivative [Line Items]
Unrealized (loss) gain on qualifying cash flow hedging instruments	$ (19,576)	$ 6,955	$ (71,828)	$ 16,631
Interest Expense
Derivative [Line Items]
Unrealized (loss) gain on qualifying cash flow hedging instruments		1,437		6,527
Effective Portion Recognized in AOCI	(2,244)		(9,646)
Effective Portion Reclassified from AOCI	$ 22		$ 430
Ineffective Portion		0		740
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net		$ (37)		$ (211)

The effective portion of net gain (loss) reclassified from accumulated other comprehensive income into income on derivative instruments designated and qualifying as hedging instruments.

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The portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments representing (a) the amount of the hedge ineffectiveness and (b) the amount, if any, excluded from the assessment of hedge effectiveness.

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Amount, before tax and reclassification, of gain (loss) from derivative instrument designated and qualifying cash flow hedge included in assessment of hedge effectiveness.

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Amount, after tax, of reclassification of gain (loss) from accumulated other comprehensive income (AOCI) for derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness.

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Amount after tax of increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss).

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