Earnings per Common Share (Details) $ / shares in Units, $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2017 USD ($) $ / shares shares	Mar. 31, 2017 shares	Jun. 30, 2016 USD ($) $ / shares shares	Jun. 30, 2017 USD ($) $ / shares shares	Jun. 30, 2016 USD ($) $ / shares shares
Continuing Operations
Income from continued operations	$ 11,153		$ 8,648	$ 20,710	$ 18,112
Less: Net income attributable to non-controlling interest	657		703	1,358	1,440
Less: Income attributable to participating shares	14			22
Basic - Income from continuing operations	10,482		7,945	19,330	16,672
Discontinued Operations
Loss from discontinued operations					(351)
Basic — Net income attributable to common stockholders after allocation to participating shares	10,482		7,945	19,330	16,321
Diluted Earnings
Diluted - Income from continuing operations	10,482		7,945	19,330	16,672
Diluted — Net income attributable to SLD common stockholders after allocation to participating shares (RSUs)	$ 10,482		$ 7,945	$ 19,330	$ 16,321
Basic weighted average common shares outstanding | shares	30,768,900		25,870,420	30,659,958	25,870,453
Effect of dilutive securities — Unvested participating shares | shares	432			217
Diluted — Average shares outstanding | shares	30,769,332		25,870,420	30,660,175	25,870,453
Earnings (loss) per share
Continuing operations, Basic | $ / shares	$ 0.34		$ 0.31	$ 0.63	$ 0.64
Discontinued operations, Basic | $ / shares					(0.01)
Continuing operations, Diluted | $ / shares	$ 0.34		$ 0.31	$ 0.63	0.64
Discontinued operations, Diluted | $ / shares					$ (0.01)
Conversion ratio				0.8356
RSU
Earnings (loss) per share
Securities excluded from the computation of diluted shares | shares		10,000		10,000