Derivative Contracts - Impact of Hedges on AOCI and Statements of Operations (Details) - Cash Flow Hedging [Member] - USD ($) $ in Thousands	9 Months Ended
Sep. 30, 2016	Sep. 30, 2015
Derivatives Designated as Cash Flow Hedges [Member]
Derivative [Line Items]
Loss recorded in AOCI (effective portion)	$ (37,927)	$ (21,975)
Loss reclassified from AOCI (effective portion)	(21,361)	(27,897)
Derivatives Designated as Cash Flow Hedges [Member] \| Interest Expense [Member]
Derivative [Line Items]
Gain (loss) recorded as interest expense (ineffective portion)	0	0
Derivatives Designated as Cash Flow Hedges [Member] \| Fund X [Member]
Derivative [Line Items]
Loss recorded in AOCI (effective portion)	(814)	(2,483)
Loss reclassified from AOCI (effective portion)	(311)	(709)
Derivatives Not Designated as Cash Flow Hedges [Member] \| Interest Expense [Member]
Derivative [Line Items]
Gain (loss) recorded as interest expense	$ 0	$ 0

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5624171-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4D
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5624177-113959

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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5624171-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 25
-Section 50
-Paragraph 1
-Subparagraph (a)(1),(2)
-URI http://asc.fasb.org/extlink&oid=6886632&loc=d3e76258-113986

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- Definition

The effective portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments that was recognized in other comprehensive income during the current period.

+ References

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