Shareholders' Equity, Noncontrolling Interests and Other Comprehensive Income - Noncontrolling Interest (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			$ 648,440
Net income (loss)	$ (2,270)	$ 6,108	(6,430)	$ 26,079
Conversion of OP Units to Common Shares by limited partners of the Operating Partnership			0	0
Other comprehensive income - unrealized gain on valuation of swap agreements	2,950	(2,124)	8,603	(2,008)
Reclassification of realized interest on swap agreements	109	$ 930	472	1,903
Noncontrolling interest contributions			6,550	20,505
Noncontrolling interest distributions			(15,640)	(4,507)
Employee Long-term Incentive Plan Unit Awards			6,113	7,002
Rebalancing adjustment			0	$ 0
Ending Balance	$ 619,874		$ 619,874
Distributions declared (in dollars per share)			$ 0.54	$ 0.52
Conversion of Common OP Units to Common Shares by limited partners of the Operating Partnership (in shares)	63,931	41,166	63,931	41,166
LTIP Units
Increase (Decrease) in Stockholders' Equity [Roll Forward]
LTIP units outstanding (in shares)	2,606,221		2,606,221		2,274,147
Operating Partnership, as General Partner or Managing Member
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Series A Preferred OP Units (in shares)	3,331,440		3,331,440		3,328,873
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
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)	136,593		136,593		136,593
Noncontrolling Interests
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			$ 648,440	$ 589,548
Distributions declared of $0.54 and $0.52 per Common OP Unit for six months ended June 30, 2018 and 2017, respectively			(3,434)	(3,207)
Net income (loss)			(21,514)	(1,612)
Conversion of OP Units to Common Shares by limited partners of the Operating Partnership			(1,123)	(730)
Other comprehensive income - unrealized gain on valuation of swap agreements			1,358	(747)
Reclassification of realized interest on swap agreements			193	364
Noncontrolling interest contributions			6,550	20,505
Noncontrolling interest distributions			(15,640)	(4,507)
Employee Long-term Incentive Plan Unit Awards			5,842	6,662
Rebalancing adjustment			(798)	3,927
Ending Balance	$ 619,874	$ 610,203	619,874	610,203
Noncontrolling Interests | Restatement Adjustment
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Ending Balance	(798)		(798)
Noncontrolling Interests | Noncontrolling Interests in Partially-Owned Affiliates
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			545,519	494,126
Distributions declared of $0.54 and $0.52 per Common OP Unit for six months ended June 30, 2018 and 2017, respectively			0	0
Net income (loss)			(22,759)	(3,532)
Conversion of OP Units to Common Shares by limited partners of the Operating Partnership			0	0
Other comprehensive income - unrealized gain on valuation of swap agreements			930	(676)
Reclassification of realized interest on swap agreements			174	277
Noncontrolling interest contributions			6,550	20,505
Noncontrolling interest distributions			(15,640)	(4,507)
Employee Long-term Incentive Plan Unit Awards			0	0
Rebalancing adjustment				0
Ending Balance	514,774	506,193	514,774	506,193
Noncontrolling Interests | Noncontrolling Interests in Partially-Owned Affiliates | Restatement Adjustment
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Ending Balance	0		0
Noncontrolling Interests | Operating Partnership, as General Partner or Managing Member
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			102,921	95,422
Distributions declared of $0.54 and $0.52 per Common OP Unit for six months ended June 30, 2018 and 2017, respectively			(3,434)	(3,207)
Net income (loss)			1,245	1,920
Conversion of OP Units to Common Shares by limited partners of the Operating Partnership			(1,123)	(730)
Other comprehensive income - unrealized gain on valuation of swap agreements			428	(71)
Reclassification of realized interest on swap agreements			19	87
Noncontrolling interest contributions			0	0
Noncontrolling interest distributions			0	0
Employee Long-term Incentive Plan Unit Awards			5,842	6,662
Rebalancing adjustment				3,927
Ending Balance	105,100	$ 104,010	105,100	$ 104,010
Noncontrolling Interests | Operating Partnership, as General Partner or Managing Member | Restatement Adjustment
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Ending Balance	$ (798)		$ (798)