Earnings per Share and Unit (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Document Fiscal Year Focus									2017
Numerator [Abstract]
Net income (loss) attributable to common stockholders	$ 85,138	$ 59,666	$ 48,368	$ (33,223)	$ 55,868	$ 5,305	$ 34,810	$ 47,877
Income per common share - basic (note 13):
Continuing operations (in dollars per share)	$ 0.50	$ 0.35	$ 0.28	$ (0.26)	$ 0.53	$ 0.05	$ 0.36	$ 0.49
Income per common share - diluted (note 13):
Continuing operations (in dollars per share)					$ 0.53	$ 0.05	$ 0.35	$ 0.49
Earnings Per Common Unit - Diluted [Abstract]
Current Fiscal Year End Date									--12-31
Weighted Average Limited Partnership Units Outstanding, Basic									295,054	154,170	154,170
Parent Company [Member]
Numerator [Abstract]
Net income (loss) attributable to common stockholders									$ 159,949	$ 143,860	$ 128,994
Denominator [Abstract]
Weighted average common shares/units outstanding for basic EPS/EPU									159,536,000	100,863,000	94,391,000
Weighted average common shares/units outstanding for diluted EPS/EPU									159,960,000	101,285,000	94,856,000
Income per common share - basic (note 13):
Continuing operations (in dollars per share)									$ 1.00	$ 1.43	$ 1.37
Income per common share - diluted (note 13):
Continuing operations (in dollars per share)									$ 1.00	$ 1.42	$ 1.36
Partnership Interest [Member]
Denominator [Abstract]
Weighted average common shares/units outstanding for basic EPS/EPU									159,831,000	101,017,000	94,546,000
Weighted average common shares/units outstanding for diluted EPS/EPU									160,255,000	101,439,000	95,011,000
Income per common share - basic (note 13):
Continuing operations (in dollars per share)									$ 1.00	$ 1.43	$ 1.37
Income per common share - diluted (note 13):
Continuing operations (in dollars per share)									1.00	1.42	1.36
Earnings Per Common Unit, Basic [Abstract]
Continuing operations (in dollars per share)									1.00	1.43	1.37
Earnings Per Common Unit - Diluted [Abstract]
Continuing operations (in dollars per share)									$ 1.00	$ 1.42	$ 1.36
Continuing operations | Parent Company [Member]
Numerator [Abstract]
Net income (loss) attributable to common stockholders									$ 159,949	$ 143,860	$ 128,994
Net (loss) income for common stockholders - diluted									159,949	143,860	128,994
Continuing operations | Partnership Interest [Member]
Numerator [Abstract]
Net income (loss) attributable to common stockholders									160,337	144,117	129,234
Net (loss) income for common stockholders - diluted									$ 160,337	$ 144,117	$ 129,234