It represents the percentage of land leased during period.

No definition available.

Name:	gkk_PercentageOfLandLeased
Namespace Prefix:	gkk_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The cash inflow from the sale of unencumbered properties in joint venture.

+ References

No definition available.

+ Details

Name:	gkk_ProceedsFromSaleOfUnencumberedPropertiesInJointVenture
Namespace Prefix:	gkk_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Area of land held.

+ References

No definition available.

+ Details

Name:	us-gaap_AreaOfLand
Namespace Prefix:	us-gaap_
Data Type:	num:areaItemType
Balance Type:	na
Period Type:	instant

- Definition

The cash outflow from the acquisition of a piece of land, anything permanently fixed to it, including buildings, structures on it and so forth; includes real estate intended to generate income for the owner; excludes real estate acquired for use by the owner.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 13

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3213-108585

+ Details

Name:	us-gaap_PaymentsToAcquireRealEstate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Repayment received or receivable for expenses incurred on behalf of a client or customer, other than those reimbursements received by landlords from tenants.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.1)

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 605

-SubTopic 45

-Section 45

-Paragraph 23

-URI http://asc.fasb.org/extlink&oid=21915142&loc=d3e60722-111653

+ Details

Name:	us-gaap_ReimbursementRevenue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Subsequent Events (Details Textual) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended			6 Months Ended	1 Months Ended		1 Months Ended
	Jun. 30, 2013 sqft	Jun. 30, 2012	Jun. 30, 2013 sqft	Jun. 30, 2012	Jun. 30, 2013 Bank Of America [Member]	Jun. 30, 2013 Subsequent Event [Member]	Jul. 31, 2013 Subsequent Event [Member] Bank Of America [Member]	May 06, 2013 Subsequent Event [Member] Bank Of America [Member]	Aug. 31, 2013 Subsequent Event [Member] Multi-tenanted Bank [Member]	Aug. 01, 2013 Subsequent Event [Member] Multi-tenanted Bank [Member] sqft
Business Acquisition Area of Land	1,600,000		1,600,000							42,000
Proceeds From Sale Of Unencumbered Properties In Joint Venture							$ 2,000
Acquisition of real estate			125,510	0					4,900
Percentage Of Land Leased	100.00%		100.00%		90.00%			100.00%
Expense reimbursements	$ 196	$ 0	$ 304	$ 0		$ 4,745