国产福利资源在线播放 Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies - Narrative (Details)	12 Months Ended
	Dec. 31, 2018 USD ($) financial_institutions	Dec. 31, 2017 USD ($)	Dec. 31, 2016
Easement agreements, term	10 years	听	听
Unrecognized tax benefits	$ 0	$ 0	听
Cash and Cash Equivalents \| Customer Concentration Risk	听	听	听
Number of customers \| financial_institutions	2	听	听
Sales Revenue, Net \| Customer Concentration Risk	听	听	听
Concentration risk, percentage	31.30%	26.50%	23.70%
Accounting Standards Update 2018-02	听	听	听
Cumulative adjustment from AOCI	$ 200,000	听	听
Maximum	听	听	听
Royalty payment arrangement, term	3 months	听	听
Lease terms of payment arrangements	10 years	听	听
Minimum	听	听	听
Royalty payment arrangement, term	1 month	听	听
Lease terms of payment arrangements	1 month	听	听