Related Party Transactions - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Related Party Transaction [Line Items]
Due from affiliates	$ 27,327,000		$ 27,327,000					$ 32,554,000
Hunt Utility Services, LLC
Related Party Transaction [Line Items]
Payment for management fee			10,500,000	$ 6,800,000
Prepaid management fee	0		0
Accrued management fee	$ 0		$ 0					3,500,000
Management fee						$ 14,000,000	$ 13,100,000
Management agreement expiration date			Dec. 31, 2019
Agreement successive renewal terms			5 years
Management fee, description			The base fee for each twelve month period beginning each April 1 thereafter will equal 1.50% of our total equity as of December 31 of the immediately preceding year, subject to a $30.0 million cap
Investment management fee equity multiplier	1.50%		1.50%
Management fee cap	$ 30,000,000		$ 30,000,000
Hunt Utility Services, LLC | Scenario, Forecast
Related Party Transaction [Line Items]
Management fee					$ 14,200,000
Maximum | Hunt Utility Services, LLC
Related Party Transaction [Line Items]
Reimbursement of annual software license and maintenance fees and other expenses			200,000	100,000
Sharyland
Related Party Transaction [Line Items]
Lease revenue from related party	40,400,000	$ 33,800,000	80,000,000	67,500,000
Deferred rent liability	23,000,000		23,000,000					15,600,000
Payments to acquire plant, and equipment			93,900,000	$ 120,100,000
Accounts payable and accrued liabilities	9,500,000		9,500,000					13,700,000
Due from affiliates	$ 27,300,000		$ 27,300,000					$ 32,600,000