Acquisitions - Acquisition of Major Energy Companies (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2016		Sep. 30, 2016	Dec. 31, 2015	[1]	Dec. 31, 2014	Dec. 31, 2013
Business Acquisition [Line Items]
Goodwill	$ 79,147	[1]		$ 18,379		$ 0	$ 0
National Gas & Electric, LLC | Major Energy Companies
Business Acquisition [Line Items]
Cash	17,368		$ 17,368
Property and equipment	14		14
Non-current deferred tax assets	1,042		1,042
Goodwill	34,728		35,137
Net working capital, net of cash acquired	(6,746)		(6,345)
Fair value of derivative liabilities	(7,260)		(7,260)
Total	68,390		69,200
Q4 2016 Adjustments
Goodwill	(409)
Net working capital, net of cash acquired	(401)
Total	(810)
Customer Relationships— Acquired | National Gas & Electric, LLC | Major Energy Companies
Business Acquisition [Line Items]
Intangible assets - customer relationships & non-compete agreements	24,271		24,271
Trademarks | National Gas & Electric, LLC | Major Energy Companies
Business Acquisition [Line Items]
Other assets - trademarks	$ 4,973		$ 4,973

[1] See Note 4 "Equity" for disclosure of our variable interest entity in Spark HoldCo, LLC.