Significant Accounting Policies (Details Textual) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Properties Reclassified Impairment Charges	$ 0		$ 0
Investment in joint ventures	49,920		49,920		72,742
Real Estate Held-for-sale	0		0		88,806
Allowance for Doubtful Accounts Receivable	17		17		211
Minimum Percentage Of Ordinary Taxable Income To Stockholders			90.00%
Assets held-for-sale, net (includes consolidated VIEs of $0 and $1,913,353, respectively)	0		0		1,952,264
Amortization of Intangible Assets	347	21	442	35
Depreciation and Amortization, Discontinued Operations	0	21	3	35
Amortization Of Off Market Lease Unfavorable and Off Market Lease Favorable	65	56	83	113
Amortization Of Intangible Assets and Liabilities Discontinued Operations	0	56	34	113
Less: Unvested restricted shares (in shares)	(766,731)	(541,667)	699,876	(541,667)	1,383,388
Management Fee Percentage	81.00%	100.00%	76.00%	100.00%
Income Tax Expense (Benefit)	4,441	2,107	4,846	3,419
Income Tax Expense (Benefit), Continuing Operations, Discontinued Operations, Extraordinary Items	0	0	2,515
Percentage Of Rental Revenue	27.00%		44.00%
Finite-Lived Intangible Asset, Useful Life			15 years
Impairment Of Real Estate		2,639	9,323	39,713
Finite-Lived Intangible Assets, Accumulated Amortization	556		556		42
Asset management incentive fee			5,700
Asset management business description			The Management Agreement provides for an incentive fee, or the Threshold Value Profits Participation, in an amount equal to the greater of: (a) $3,500 or (b) 10% of the amount, if any, by which the portfolio equity value exceeds $375,000 (as adjusted for future cash contributions into, and distributions out of, KBSAS by KBS REIT).  The Threshold Value Profits Participation is capped at a maximum of $12,000 and is payable 60 days after the earlier to occur of June 30, 2014 (or March 31, 2015 upon satisfaction of certain extension conditions including the payment by KBSAS of a $750 extension fee) and the date on which KBSAS, directly or indirectly sells, conveys or otherwise transfers at least 90% of the KBS portfolio.
In Place Leases [Member] | Minimum [Member]
Finite-Lived Intangible Asset, Useful Life			6 years
In Place Leases [Member] | Maximum [Member]
Finite-Lived Intangible Asset, Useful Life			20 years
Leases, Acquired-in-Place [Member]
Finite-Lived Intangible Assets, Accumulated Amortization	469		469		359
Above Market Leases [Member]
Finite-Lived Intangible Assets, Accumulated Amortization	87		87		48
Assets Held-for-sale [Member]
Finite-Lived Intangible Assets, Accumulated Amortization	0		0		365
Liabilities Held For Sale [Member]
Finite Lived Intangible Liabilities Accumulated Amortization	0		0		1,391
Below Market Lease [Member]
Finite Lived Intangible Liabilities Accumulated Amortization	$ 121		$ 121		$ 1,395
Building [Member]
Property, Plant and Equipment, Useful Life			40 years
Building Equipment And Fixtures [Member]
Finite-Lived Intangible Asset, Useful Life			10 years