Derivative Contracts - Counterparty Credit Risk (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Fair value of derivatives in an asset position	$ 16,788	$ 73,414
Interest Rate Swap \| Derivatives Designated as Cash Flow Hedges \| Cash Flow Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Fair value of derivatives in an asset position	$ 18,749	76,021
Percent of notional amount related to the Fund	100.00%
Interest Rate Swap \| Derivatives Designated as Cash Flow Hedges \| Cash Flow Hedging \| Unconsolidated Funds
Derivative Instruments, Gain (Loss) [Line Items]
Fair value of derivatives in an asset position	$ 1,598	$ 12,576
Percent of notional amount related to the Fund	100.00%

Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226008-175313

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=118260190&loc=d3e13433-108611

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

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Balance Type:	debit
Period Type:	instant