Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Percent			21.00%
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent				34.00%
Net deferred income tax liabilities	$ 28,819		$ 28,819		$ 28,763
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration	8,000		8,000		8,000
Deferred Tax Liabilities, Other					20,900
Deferred Tax Liabilities, Goodwill and Intangible Assets	20,900		20,900
Deferred Tax Liabilities, Regulatory Assets and Liabilities					100
Unrecognized Tax Benefits	1,400		1,400		1,400
Income Tax Examination, Penalties and Interest Expense	100	$ 200	100	$ 400
Income Tax Examination, Penalties and Interest Accrued	$ 1,000		$ 1,000		$ 900