Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies - Equity Method Investment (Details)

v3.22.4
Summary of Significant Accounting Policies - Equity Method Investment (Details) - NRP
Dec. 31, 2017
USD ($)
Accounting Policies [Line Items]  
Ownership percentage 25.00%
Equity method investment $ 125,000