Acquisitions - Acquisition of Provider Companies - Narrative (Details)		12 Months Ended
	Aug. 01, 2016 USD ($) payment $ / shares shares	Dec. 31, 2017 USD ($)		Dec. 31, 2016 USD ($)		Dec. 31, 2015 USD ($)	[3]	Aug. 23, 2016 $ / shares
Business Acquisition [Line Items]
Installment payment		$ 152,939,000	[1]	$ 66,652,000	[2]	$ 49,826,000
Common Class B
Business Acquisition [Line Items]
Issuance of stock to affiliates		0	[1]	40,000,000	[2]	0
Share price (in dollars per share) | $ / shares	$ 10							$ 10
Provider Companies
Business Acquisition [Line Items]
Purchase price	$ 34,100,000
Initial working capital estimate	1,300,000
Installment consideration payment	$ 3,800,000	0	[1]	1,890,000	[2]	$ 0
Frequency of monthly payments | payment	10
Installment payment	$ 400,000
Revenue				46,800,000
Operating loss				$ 12,800,000
Provider Companies | Common Class B
Business Acquisition [Line Items]
Shares issued (shares) | shares	1,399,484
Issuance of stock to affiliates	$ 14,000,000
Revolving Credit Facility | Acquisition Line | Provider Companies
Business Acquisition [Line Items]
Borrowing from credit facility	10,600,000
Recurring | Provider Companies
Business Acquisition [Line Items]
Contingent consideration—earnout obligations incurred in connection with the acquisitions		$ 4,800,000
Maximum | Provider Companies
Business Acquisition [Line Items]
Earnout amount	$ 9,000,000.0

[1] Financial information has been recast to include results attributable to the acquisition of Perigee Energy, LLC by an affiliate on February 3, 2017. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.

[2] Financial information has been recast to include results attributable to the acquisition of the Major Energy Companies from an affiliate on April 15, 2016. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.

[3] Financial information has been recast to include results attributable to the acquisition of Oasis Power Holdings LLC by an affiliate on May 12, 2015. See Note 2 "Basis of Presentation and Summary of Significant Accounting Policies" for further discussion.