Segment Information (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Segment Reporting Information [Line Items]
Income from office and parking properties									$ 206,739,000		$ 147,290,000		$ 93,548,000
Management company income									19,778,000		16,896,000		1,652,000
Property operating expenses									(80,748,000)		(60,733,000)		(40,408,000)
Depreciation and amortization									(81,537,000)		(56,522,000)		(28,496,000)
Management company expenses									(17,237,000)		(13,337,000)		(2,756,000)
Income tax expense	(118,000)	7,000	11,000	(161,000)	(6,000)	174,000	(224,000)	0	(261,000)		(56,000)		(2,000)
General and administrative expenses									(16,420,000)		(18,805,000)		(15,318,000)
Acquisition costs									(2,791,000)		(17,219,000)		(846,000)
Interest and other income	67,000	64,000	44,000	97,000	90,000	87,000	437,000	324,000	272,000		938,000		1,487,000
Equity in earnings of unconsolidated joint ventures					(8,000)	(14,000)	44,000	35,000	0		57,000		326,000
Interest expense	(9,033,000)	(8,521,000)	(8,536,000)	(9,244,000)	(8,660,000)	(8,876,000)	(7,668,000)	(6,408,000)	(35,334,000)		(31,612,000)		(20,271,000)
Adjustment for noncontrolling interest-unit holders									269,000		(5,000)		0
Adjustment for noncontrolling interest - real estate partnerships									3,317,000		85,105,000		10,789,000
Income (loss) from discontinued operations	(85,000)	(330,000)	(524,000)	3,393,000	(56,279,000)	(131,780,000)	(3,965,000)	(2,790,000)	2,454,000		(194,813,000)		(10,881,000)
Impairment loss on real estate									(9,200,000)		(6,420,000)		0
Impairment loss on mortgage loan receivable									0		(9,235,000)		0
Impairment loss on management contracts and goodwill									(41,967,000)		0		0
Gain on sale of real estate from discontinued operations									12,939,000		17,825,000		8,518,000
Gain on sale of real estate and other assets									548,000		743,000		40,000
Change in fair value of contingent consideration									(216,000)		13,000,000		0
Dividends on preferred stock	(2,711,000)	(2,711,000)	(3,721,000)	(2,711,000)	(2,711,000)	(2,711,000)	(2,443,000)	(2,187,000)	(10,843,000)		(10,052,000)		(6,325,000)
Dividends on convertible preferred stock									(1,011,000)
Net income (loss) attributable to common stockholders	(51,713,000)	(582,000)	(948,000)	1,994,000	(59,763,000)	(55,738,000)	(14,673,000)	(6,782,000)	(51,249,000)		(136,955,000)		(8,943,000)
Depreciation and amortization									81,537,000		56,522,000		28,496,000
Depreciation and amortization - discontinued operations									933,000		54,628,000		63,815,000
Adjustment for noncontrolling - unit holders									(269,000)		5,000		0
Total assets	1,906,611,000				1,636,311,000				1,906,611,000		1,636,311,000		1,603,682,000
Office and parking properties	1,562,717,000				921,937,000				1,562,717,000		921,937,000		1,389,767,000
Assets held for sale					382,789,000						382,789,000
Capital expenditures									37,506,000		58,758,000		49,760,000
Office Properties [Member]
Segment Reporting Information [Line Items]
Income from office and parking properties									206,739,000	[1]	147,290,000	[1]	93,548,000	[1]
Management company income									0		0		0
Property operating expenses									(80,748,000)	[2]	(60,733,000)	[2]	(40,408,000)	[2]
Depreciation and amortization									(81,537,000)		(56,522,000)		(28,496,000)
Management company expenses									0		0		0
Income tax expense									0		0		0
General and administrative expenses									0		0		0
Acquisition costs									(2,791,000)		(1,225,000)		(846,000)
Interest and other income									0		0		0
Equity in earnings of unconsolidated joint ventures											57,000		326,000
Interest expense									(31,394,000)	[3]	(24,888,000)	[3]	(14,255,000)	[3]
Adjustment for noncontrolling interest-unit holders									0		0
Adjustment for noncontrolling interest - real estate partnerships									3,317,000		85,105,000		10,789,000
Income (loss) from discontinued operations									2,454,000		(194,813,000)		(10,881,000)
Impairment loss on real estate									(9,200,000)		(6,420,000)
Impairment loss on mortgage loan receivable											0
Impairment loss on management contracts and goodwill									0
Gain on sale of real estate from discontinued operations									12,939,000		17,825,000		8,518,000
Gain on sale of real estate and other assets									48,000		743,000		40,000
Change in fair value of contingent consideration									0		0
Dividends on preferred stock									0		0		0
Dividends on convertible preferred stock									0
Net income (loss) attributable to common stockholders									19,827,000		(93,581,000)		18,335,000
Adjustment for noncontrolling - unit holders									0		0
Total assets	1,832,493,000				1,532,803,000				1,832,493,000		1,532,803,000		1,590,545,000
Office and parking properties	1,562,717,000				921,937,000				1,562,717,000		921,937,000		1,389,767,000
Assets held for sale					382,789,000						382,789,000
Capital expenditures									37,506,000	[4]	58,758,000	[4]	49,760,000	[4]
Unallocated and Other [Member]
Segment Reporting Information [Line Items]
Income from office and parking properties									0		0		0
Management company income									19,778,000		16,896,000		1,652,000
Property operating expenses									0		0		0
Depreciation and amortization									0		0		0
Management company expenses									(17,237,000)		(13,337,000)		(2,756,000)
Income tax expense									(261,000)		(56,000)		(2,000)
General and administrative expenses									(16,420,000)		(18,805,000)		(15,318,000)
Acquisition costs									0		(15,994,000)		0
Interest and other income									272,000		938,000		1,487,000
Equity in earnings of unconsolidated joint ventures											0		0
Interest expense									(3,940,000)	[3]	(6,724,000)	[3]	(6,016,000)	[3]
Adjustment for noncontrolling interest-unit holders									269,000		(5,000)
Adjustment for noncontrolling interest - real estate partnerships									0		0		0
Income (loss) from discontinued operations									0		0		0
Impairment loss on real estate									0		0
Impairment loss on mortgage loan receivable											(9,235,000)
Impairment loss on management contracts and goodwill									(41,967,000)
Gain on sale of real estate from discontinued operations									0		0		0
Gain on sale of real estate and other assets									500,000		0		0
Change in fair value of contingent consideration									(216,000)		13,000,000
Dividends on preferred stock									(10,843,000)		(10,052,000)		(6,325,000)
Dividends on convertible preferred stock									(1,011,000)
Net income (loss) attributable to common stockholders									(71,076,000)		(43,374,000)		(27,278,000)
Adjustment for noncontrolling - unit holders									(269,000)		5,000
Total assets	74,118,000				103,508,000				74,118,000		103,508,000		13,137,000
Office and parking properties	0				0				0		0		0
Assets held for sale					0						0
Capital expenditures									$ 0		$ 0		$ 0

[1] (a) Included in income from office and parking properties are rental revenues, customer reimbursements, parking income and other income.

[2] (b) Included in property operating expenses are real estate taxes, insurance, contract services, repairs and maintenance and property operating expenses.

[3] (c) Interest expense for office properties represents interest expense on property secured mortgage debt. It does not include interest expense on the Company's unsecured credit facility, which is included in "Unallocated and Other".

[4] (d) Capital expenditures include building improvements, tenant improvements and leasing costs.