Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
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-Article 12
-Section 13
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Fixed interest rate related to the interest rate derivative.

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The net gain (loss) during the reporting period due to ineffectiveness in interest rate cash flow hedges. Recognized in earnings.

+ References

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- Definition

Fair value as of the balance sheet date of all interest rate derivative liabilities designated as cash flow hedging instruments.

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- Definition

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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Derivative Financial Instruments - Australia Ravenhall (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 AUD ($)
Derivative [Line Items]
Unrealized gain, net of tax, related to cash flow hedge	$ 1,536,000	$ 1,740,000	$ 4,550,000	$ 2,556,000
Ravenhall, Australia
Derivative [Line Items]
Ineffective portion of Cash Flow Hedge interest rate swap			0
Ravenhall, Australia \| Other Noncurrent Liabilities
Derivative [Line Items]
Fair value of the swap liability	$ 8,600,000		$ 8,600,000
Ravenhall, Australia \| Operating phase \| Interest Rate Swap
Derivative [Line Items]
Fixed interest rate on derivative	4.20%		4.20%		4.20%
Notional amount coincide with the terms of the non-recourse debt	$ 330,200,000		$ 330,200,000		$ 457
Ravenhall, Australia \| Cash Flow Hedge
Derivative [Line Items]
Unrealized gain, net of tax, related to cash flow hedge			$ 4,600,000