Income Taxes - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2017	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Federal tax rate				34.00%	21.00%
Deferred tax asset, increase (decrease), amount		$ 800
Net deferred income tax liabilities	$ 28,984				$ 28,984		$ 28,537
Deferred tax assets, operating loss carryforwards, subject to expiration	8,000				8,000		8,000
Goodwill and intangible assets	21,700				21,700
Deferred income tax assets, state taxes	600				600		500
Deferred tax liabilities, other	100				100		21,100
Regulatory assets and liabilities							100
Unrecognized tax benefits			$ 1,400			$ 1,400	1,400
Income tax expense recorded	100		$ 100		100	$ 100
Interest and penalties paid	$ 1,200				$ 1,200		$ 1,100