Shareholders' Equity, Noncontrolling Interests and Other Comprehensive Income - Noncontrolling Interest (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended			9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Mar. 31, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance				$ 589,548
Net income (loss)	$ 13,285	$ 326		39,364	$ 100,356
Conversion of Common OP Units to Common Shares by limited partners of the Operating Partnership				0	0
Issuance of OP Units to acquire real estate					29,336
Acquisition of noncontrolling interests					(18,379)
Other comprehensive income - unrealized loss on valuation of swap agreements	(644)	1,474		(2,652)	(12,624)
Change in control of previously unconsolidated investment					(75,713)
Reclassification of realized interest on swap agreements	734	$ 1,210		2,637	3,396
Noncontrolling interest contributions				20,522	204,412
Noncontrolling interest distributions				(7,278)	(50,849)
Employee Long-term Incentive Plan Unit Awards				9,129	11,682
Rebalancing adjustment				0	0
Balance	$ 606,256			606,256		$ 589,548
Payments to noncontrolling interests				$ 12,813	$ 74,612
Distributions declared (in dollars per share)				$ 0.78	$ 0.75
Limited partners' capital account, units issued and converted (in shares)	61,150	350,240		61,150	350,240
LTIP Units
Increase (Decrease) in Stockholders' Equity [Roll Forward]
LTIP units outstanding (in shares)	2,274,147	1,997,099		2,274,147	1,997,099
Series A Preferred Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Limited partners' capital account, units issued and converted (in shares)	1,392			1,392
Fund II
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Additional ownership interest acquired			8.30%
Payments to noncontrolling interests			$ 18,400
Equity Interest Held By Operating Partnership			28.33%
Operating Partnership, as General Partner or Managing Member
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Series A Preferred OP Units (in shares)	3,341,397	3,308,875		3,341,397	3,308,875
Equity Interest Held By Operating Partnership				95.00%		95.00%
Operating Partnership, as General Partner or Managing Member | Series A Preferred Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Series A Preferred OP Units (in shares)	188	188		188	188
Operating Partnership, as General Partner or Managing Member | Series C Preferred Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Series A Preferred OP Units (in shares)	140,343	141,593		140,343	141,593
Noncontrolling Interests
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance			$ 420,866	$ 589,548	$ 420,866	$ 420,866
Distributions declared of $0.78 and $0.75 per Common OP Unit for Nine Months Ended September 30, 2017 and 2016				(4,805)	(4,398)
Net income (loss)				(1,194)	47,401
Conversion of Common OP Units to Common Shares by limited partners of the Operating Partnership				(1,086)	(7,875)
Issuance of OP Units to acquire real estate					29,336
Acquisition of noncontrolling interests					(25,925)
Other comprehensive income - unrealized loss on valuation of swap agreements				(794)	(1,273)
Change in control of previously unconsolidated investment					(75,713)
Reclassification of realized interest on swap agreements				534	426
Noncontrolling interest contributions				20,522	204,412
Noncontrolling interest distributions				(7,278)	(50,849)
Employee Long-term Incentive Plan Unit Awards				8,704	10,983
Rebalancing adjustment				2,105	(35,254)
Balance	$ 606,256	$ 512,137		606,256	512,137	589,548
Noncontrolling Interests | Restatement Adjustment
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance	2,105			2,105
Noncontrolling Interests | Noncontrolling Interests in Partially-Owned Affiliates
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance			324,526	494,126	324,526	324,526
Distributions declared of $0.78 and $0.75 per Common OP Unit for Nine Months Ended September 30, 2017 and 2016				0	0
Net income (loss)				(4,010)	43,644
Conversion of Common OP Units to Common Shares by limited partners of the Operating Partnership				0	0
Issuance of OP Units to acquire real estate					0
Acquisition of noncontrolling interests					(25,925)
Other comprehensive income - unrealized loss on valuation of swap agreements				(726)	(633)
Change in control of previously unconsolidated investment					(75,713)
Reclassification of realized interest on swap agreements				418	260
Noncontrolling interest contributions				20,522	204,412
Noncontrolling interest distributions				(7,278)	(50,849)
Employee Long-term Incentive Plan Unit Awards				0	0
Rebalancing adjustment					0
Balance	503,052	419,722		503,052	419,722	494,126
Noncontrolling Interests | Noncontrolling Interests in Partially-Owned Affiliates | Restatement Adjustment
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance	0			0
Noncontrolling Interests | Operating Partnership, as General Partner or Managing Member
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance			$ 96,340	95,422	96,340	96,340
Distributions declared of $0.78 and $0.75 per Common OP Unit for Nine Months Ended September 30, 2017 and 2016				(4,805)	(4,398)
Net income (loss)				2,816	3,757
Conversion of Common OP Units to Common Shares by limited partners of the Operating Partnership				(1,086)	(7,875)
Issuance of OP Units to acquire real estate					29,336
Acquisition of noncontrolling interests					0
Other comprehensive income - unrealized loss on valuation of swap agreements				(68)	(640)
Change in control of previously unconsolidated investment					0
Reclassification of realized interest on swap agreements				116	166
Noncontrolling interest contributions				0	0
Noncontrolling interest distributions				0	0
Employee Long-term Incentive Plan Unit Awards				8,704	10,983
Rebalancing adjustment					(35,254)
Balance	103,204	$ 92,415		103,204	$ 92,415	$ 95,422
Noncontrolling Interests | Operating Partnership, as General Partner or Managing Member | Restatement Adjustment
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance	$ 2,105			$ 2,105