Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2016	Dec. 31, 2015
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	50,000,000	50,000,000
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	250,000,000	250,000,000
Common stock, shares issued	75,914,763	66,105,650
Common stock, shares outstanding	75,914,763	66,105,650
General Partners' Capital Account, Units Issued	662,373	662,373
General partners' capital, units outstanding	662,373	662,373
Series A cumulative redeemable perpetual preferred units [Member]
Limited partners' capital, common units issued	0	7,400,000
Limited partners' capital, common units outstanding	0	7,400,000
Series B cumulative redeemable perpetual preferred units [Member]
Limited partners' capital, common units issued	0	6,650,000
Limited partners' capital, common units outstanding	0	6,650,000
Series C cumulative redeemable perpetual preferred units [Member]
Limited partners' capital, common units issued	8,050,000	0
Limited partners' capital, common units outstanding	8,050,000	0
Limited partners' common units [Member]
Limited partners' capital, common units issued	75,252,390	65,443,277
Limited partners' capital, common units outstanding	75,252,390	65,443,277
Series A cumulative redeemable perpetual preferred stock [Member]
Preferred stock, shares issued	0	7,400,000
Preferred stock, shares outstanding	0	7,400,000
Series B cumulative redeemable perpetual preferred stock [Member]
Preferred stock, shares issued	0	6,650,000
Preferred stock, shares outstanding	0	6,650,000
Series C cumulative redeemable perpetual preferred stock [Member]
Preferred stock, shares issued	8,050,000	0
Preferred stock, shares outstanding	8,050,000	0