14. Earnings Per Unit of the Operating Partnership (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Earnings per unit of the Operating Partnership [Line Items]
Weighted average common units – basic (includes redeemable partnership units and units of general and limited partners)	87,284,564	80,599,199	81,053,127
Effect of dilutive securities	835,872	0	600,271
Weighted average common units – diluted	88,120,436	80,599,199	81,653,398
Net income Loss attributable to common units, basic	$ 148,213	$ (31,331)	$ 97,366
Net income allocated to unvested restricted units	(628)	(599)	(484)
Net income attributable to common units, adjusted	$ 147,585	$ (31,930)	$ 96,882
Earnings per unit, basic	$ 1.69	$ (0.40)	$ 1.19
Earnings per unit, diluted	$ 1.67	$ (0.40)	$ 1.18
Subsidiaries [Member]
Earnings per unit of the Operating Partnership [Line Items]
Net income Loss attributable to common units, basic	$ 148,213	$ (31,331)	$ 97,366
Earnings per unit, basic	$ 1.69	$ (0.40)	$ 1.19
Earnings per unit, diluted	$ 1.67	$ (0.40)	$ 1.18
Equity Option [Member]
Earnings per unit of the Operating Partnership [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	0	600,000	0
Performance Shares [Member]
Earnings per unit of the Operating Partnership [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	100,000	100,000	100,000