Earnings per Share and Unit (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Document Fiscal Year Focus									2013
Current Fiscal Year End Date									--12-31
Weighted Average Limited Partnership Units Outstanding, Basic									171,886,000	177,164,000	177,164,000
Numerator [Abstract]
Net income (loss) attributable to common stockholders	$ 46,326	$ 34,998	$ 31,864	$ 15,554	$ (37,179)	$ 11,637	$ 5,697	$ 13,181
Income (loss) per common share - basic (note 14):
Net income attributable to common stockholders (in dollars per share)	$ 0.50	$ 0.38	$ 0.35	$ 0.17	$ (0.41)	$ 0.13	$ 0.06	$ 0.14
Income (loss) per common share - diluted (note 14):
Net income (loss) attributable to common stockholders (in dollars per share)	$ 0.50	$ 0.38	$ 0.35	$ 0.17	$ (0.41)	$ 0.13	$ 0.06	$ 0.14
Parent Company [Member]
Numerator [Abstract]
Income from continuing operations									84,297	45,779	36,805
Income from discontinued operations									65,285	(21,728)	16,579
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Noncontrolling Interest									121	(43)	33
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent									65,164	(21,685)	16,546
Gain on sale of real estate									1,703	2,158	2,404
Income (Loss) from Continuing Operations Attributable to Noncontrolling Interest									1,360	385	4,385
Income (Loss) from Continuing Operations Attributable to Parent									84,640	47,552	34,824
Net income									151,285	26,209	55,788
Less: preferred stock dividends									21,062	32,531	19,675
Net income attributable to noncontrolling interests									1,481	342	4,418
Net income (loss) attributable to common stockholders									128,294	(7,236)	31,080
Less: dividends paid on unvested restricted stock									448	572	615
Net income (loss) attributable to common stockholders									128,742	(6,664)	31,695
Add: dividends paid on Treasury Method restricted stock									45	71	18
Net (loss) income for common stockholders - diluted									128,339	(7,165)	31,098
Denominator [Abstract]
Weighted average common shares/units outstanding for basic EPS/EPU									91,383,000	89,630,000	87,825,000
Incremental Common Shares Attributable to Dilutive Effect of Call Options and Warrants									2,000	0	0
Incremental shares to be issued under unvested restricted stock									24,000	39,000	10,000
Incremental shares under Forward Equity Offering									0	0	424,000
Weighted average common shares/units outstanding for diluted EPS/EPU									91,409,000	89,669,000	88,259,000
Income (loss) per common share - basic (note 14):
Continuing operations (in dollars per share)									$ 0.69	$ 0.16	$ 0.16
Discontinued operations (in dollars per share)									$ 0.71	$ (0.24)	$ 0.19
Net income attributable to common stockholders (in dollars per share)									$ 1.40	$ (0.08)	$ 0.35
Income (loss) per common share - diluted (note 14):
Continuing operations (in dollars per share)									$ 0.69	$ 0.16	$ 0.16
Discontinued operations (in dollars per share)									$ 0.71	$ (0.24)	$ 0.19
Net income (loss) attributable to common stockholders (in dollars per share)									$ 1.40	$ (0.08)	$ 0.35
Partnership Interest [Member]
Numerator [Abstract]
Income from continuing operations									84,297	45,779	36,805
Income from discontinued operations									65,285	(21,728)	16,579
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Noncontrolling Interest									121	(43)	33
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent									65,164	(21,685)	16,546
Gain on sale of real estate									1,703	2,158	2,404
Income (Loss) from Continuing Operations Attributable to Parent									84,916	47,029	38,652
Net income									151,285	26,209	55,788
Less: preferred unit distributions									21,062	31,902	23,400
Net income attributable to noncontrolling interests									1,205	865	590
Net income (loss) attributable to common stockholders									128,570	(7,130)	31,183
Net (loss) income attributable to common unit holders									129,018	(6,558)	31,798
Less: dividends paid on unvested restricted stock									448	572	615
Add: dividends paid on Treasury Method restricted stock									45	71	18
Net (loss) income for common stockholders - diluted									128,615	(7,059)	31,201
Denominator [Abstract]
Weighted average common shares/units outstanding for basic EPS/EPU									91,555,000	89,808,000	88,002,000
Incremental Common Shares Attributable to Dilutive Effect of Call Options and Warrants									2,000	0	0
Incremental shares to be issued under unvested restricted stock									24,000	39,000	10,000
Incremental shares under Forward Equity Offering									0	0	424,000
Weighted average common shares/units outstanding for diluted EPS/EPU									91,581,000	89,847,000	88,436,000
Earnings Per Common Unit, Basic [Abstract]
Continuing operations (in dollars per share)									$ 0.69	$ 0.16	$ 0.16
Discontinued operations (in dollars per share)									$ 0.71	$ (0.24)	$ 0.19
Net income attributable to common unit holders (in dollars per share)									$ 1.40	$ (0.08)	$ 0.35
Earnings Per Common Unit - Diluted [Abstract]
Continuing operations (in dollars per share)									$ 0.69	$ 0.16	$ 0.16
Discontinued operations (in dollars per share)									$ 0.71	$ (0.24)	$ 0.19
Net Income (Loss), Net of Tax, Per Outstanding Limited Partnership Unit, Diluted									$ 1.40	$ (0.08)	$ 0.35
Continuing operations | Parent Company [Member]
Numerator [Abstract]
Net income (loss) attributable to common stockholders									63,130	14,449	14,534
Net income (loss) attributable to common stockholders									63,175	14,520	14,552
Continuing operations | Partnership Interest [Member]
Numerator [Abstract]
Income (Loss) from Continuing Operations Attributable to Noncontrolling Interest									1,084	908	557
Less: dividends paid on unvested restricted stock									63,406	14,555	14,637
Add: dividends paid on Treasury Method restricted stock									$ 63,451	$ 14,626	$ 14,655