Earnings per Share and Unit (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Document Fiscal Year Focus									2016
Current Fiscal Year End Date									--12-31
Weighted Average Limited Partnership Units Outstanding, Basic									154,170	154,170	157,950
Numerator [Abstract]
Net income (loss) attributable to common stockholders	$ 55,868	$ 5,305	$ 34,810	$ 47,877	$ 17,609	$ 53,731	$ 32,480	$ 25,174
Net (loss) income attributable to common unit holders	$ 55,960	$ 5,321	$ 34,874	$ 47,962	$ 17,645	$ 53,825	$ 32,541	$ 25,223
Income per common share - basic (note 13):
Continuing operations (in dollars per share)	$ 0.53	$ 0.05	$ 0.36	$ 0.49	$ 0.18	$ 0.57	$ 0.35	$ 0.27
Income per common share - diluted (note 13):
Continuing operations (in dollars per share)					$ 0.18	$ 0.57	$ 0.34	$ 0.27
Net income (loss) attributable to common stockholders (in dollars per share)	$ 0.53	$ 0.05	$ 0.35	$ 0.49
Parent Company [Member]
Numerator [Abstract]
Less: preferred stock dividends									$ 21,062	$ 21,062	$ 21,062
Net income attributable to noncontrolling interests									2,070	2,487	1,457
Net income (loss) attributable to common stockholders									$ 143,860	$ 128,994	$ 166,328
Denominator [Abstract]
Weighted average common shares/units outstanding for basic EPS/EPU									100,863,000	94,391,000	92,370,000
Weighted average common shares/units outstanding for diluted EPS/EPU									101,285,000	94,856,000	92,404,000
Income per common share - basic (note 13):
Continuing operations (in dollars per share)									$ 1.43	$ 1.37	$ 1.80
Income per common share - diluted (note 13):
Continuing operations (in dollars per share)									$ 1.42	$ 1.36	$ 1.80
Earnings Per Common Unit - Diluted [Abstract]
Income from continuing operations									$ 119,671	$ 116,937	$ 133,770
Partnership Interest [Member]
Numerator [Abstract]
Net income attributable to noncontrolling interests									1,813	2,247	1,138
Net (loss) income attributable to common unit holders									$ 144,117	$ 129,234	$ 166,647
Denominator [Abstract]
Weighted average common shares/units outstanding for basic EPS/EPU									101,017,000	94,546,000	92,528,000
Weighted average common shares/units outstanding for diluted EPS/EPU									101,439,000	95,011,000	92,562,000
Income per common share - basic (note 13):
Continuing operations (in dollars per share)									$ 1.43	$ 1.37	$ 1.80
Income per common share - diluted (note 13):
Continuing operations (in dollars per share)									1.42	1.36	1.80
Earnings Per Common Unit, Basic [Abstract]
Continuing operations (in dollars per share)									1.43	1.37	1.80
Earnings Per Common Unit - Diluted [Abstract]
Continuing operations (in dollars per share)									$ 1.42	$ 1.36	$ 1.80
Income from continuing operations									$ 119,671	$ 116,937	$ 133,770
Continuing operations | Parent Company [Member]
Numerator [Abstract]
Net income (loss) attributable to common stockholders									143,860	128,994	165,875
Net (loss) income for common stockholders - diluted									143,860	128,994	165,938
Continuing operations | Partnership Interest [Member]
Numerator [Abstract]
Net income (loss) attributable to common stockholders									144,117	129,234	166,194
Net (loss) income for common stockholders - diluted									$ 144,117	$ 129,234	$ 166,257