Summary of Significant Accounting Policies and Practices - Variable Interest Entities (Details) - ALLO Communications [Member] - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Variable Interest Entity [Line Items]
Percent ownership in VIE	91.50%
Percent of operating decision voting power	80.00%
Potential additional percent earned by VIE management	11.50%
Line of Credit [Member]
Variable Interest Entity [Line Items]
Line of credit issued to VIE	$ 270,000,000.0
VIE line of credit amount outstanding	$ 193,100,000	$ 58,000,000