Fair Value Measurements - Fair Value Measurements - Narrative (Details) - USD ($)			1 Months Ended		3 Months Ended		9 Months Ended
	Aug. 23, 2016	Apr. 15, 2016	Jun. 30, 2017	Mar. 31, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017		Sep. 30, 2016		Jul. 01, 2017	Dec. 31, 2016	Aug. 01, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration, current liabilities					$ 4,248,000		$ 4,248,000					$ 11,827,000
Contingent consideration, noncurrent liabilities					4,458,000		4,458,000					10,826,000
Change in fair value of contingent consideration, net							(9,423,000)	[1]	$ 843,000	[2]
Major Earnout
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Accretion of contingent earnout consideration					1,000,000		3,600,000
Provider Earnout
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Accretion of contingent earnout consideration					0		100,000
Verde Earnout
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Accretion of contingent earnout consideration					100,000		$ 100,000
Major Energy Companies | Common Class B
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Share earnout maximum (in shares)	81,436
Major Energy Companies | Common Class B | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Share earnout maximum (in shares)	400,000						400,000
Business Combination, Contingent Consideration, Liability, Current | Variable Interest Entity, Primary Beneficiary
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration, current liabilities					4,248,000		$ 4,248,000					11,800,000
Contingent consideration, noncurrent liabilities												10,800,000
Business Combination, Contingent Consideration, Liability, Noncurrent | Variable Interest Entity, Primary Beneficiary
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration, noncurrent liabilities					4,500,000		4,500,000
CenStar
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent payment arrangements												4,900,000
Earnout payments							$ 0	[1]	1,343,000	[2]
Provider Companies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Earnout period (in months)							9 months
Earnout maximum					9,000,000		$ 9,000,000						$ 9,000,000
Earnout minimum					5,000,000		5,000,000
Earnout payments			$ 4,500,000	$ 1,000,000			7,738,000	[1]	0	[2]
Major Energy Companies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Earnout payments				$ 7,400,000			7,403,000	[1]	0	[2]
Major Energy Companies | Major Earnout
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Accretion of contingent earnout consideration					1,000,000		3,600,000
Major Energy Companies | National Gas & Electric, LLC
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Earnout period (in months)		33 months
Earnout maximum		$ 20,000,000.0			3,200,000		3,200,000
Verde Companies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Earnout period (in months)		18 months
Earnout maximum											$ 5,400,000
Verde Companies | Verde Earnout
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Accretion of contingent earnout consideration					100,000
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent payment arrangements					8,706,000		8,706,000					22,653,000
Fair Value, Measurements, Recurring | Major Energy Purchase Agreement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent payment arrangements					3,200,000		3,200,000					17,100,000
Fair Value, Measurements, Recurring | CenStar
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent payment arrangements					100,000		100,000					700,000
Fair Value, Measurements, Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent payment arrangements					8,706,000		8,706,000					22,653,000
Accretion of contingent earnout consideration					1,127,000	$ 0	3,787,000		$ 0
Change in fair value of contingent consideration, net							(10,231,000)
Fair Value, Measurements, Recurring | Level 3 | Major Earnout and Stock Earnout
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent payment arrangements					3,228,000		3,228,000					17,760,000
Accretion of contingent earnout consideration							3,602,000
Change in fair value of contingent consideration, net							(10,731,000)
Fair Value, Measurements, Recurring | Level 3 | Provider Earnout
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent payment arrangements												4,893,000
Accretion of contingent earnout consideration							107,000
Change in fair value of contingent consideration, net							500,000
Fair Value, Measurements, Recurring | Level 3 | Verde Earnout
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent payment arrangements												$ 0
Accretion of contingent earnout consideration							78,000
Change in fair value of contingent consideration, net							0
Fair Value, Measurements, Recurring | Level 3 | Provider Companies | Provider Earnout
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent payment arrangements					0		0
Fair Value, Measurements, Recurring | Level 3 | Verde Companies | Verde Earnout
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent payment arrangements					$ 5,478,000		$ 5,478,000

[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 by 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.