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)
-Number 210
-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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-Section 50
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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	12 Months Ended
	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2018 AUD ($)
Derivative [Line Items]
Change in fair value of derivative instrument classified as cash flow hedge	$ 6,146,000	$ 3,985,000	$ 1,820,000
Ravenhall, Australia
Derivative [Line Items]
Gain (loss) on interest rate cash flow hedge ineffectiveness	0	0
Interest Rate Swap \| Asset under Construction \| Ravenhall, Australia
Derivative [Line Items]
Fixed interest rate on cash flow interest rate derivative			3.30%
Notional amount	318,000,000			$ 450.8
Interest Rate Swap \| Operating Phase of Asset \| Ravenhall, Australia
Derivative [Line Items]
Fixed interest rate on cash flow interest rate derivative			4.20%
Cash Flow Hedging \| Ravenhall, Australia
Derivative [Line Items]
Change in fair value of derivative instrument classified as cash flow hedge	6,100,000	1,800,000	$ 4,000,000
Other Noncurrent Liabilities \| Ravenhall, Australia
Derivative [Line Items]
Value of swap liability	$ 6,800,000	$ 14,000,000