Income Taxes Narrative (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended		12 Months Ended
	Sep. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Federal tax rate	21.00%		21.00%	21.00%	21.00%	21.00%	34.00%
Deferred tax asset, increase (decrease), amount		$ 800
Net deferred income tax liabilities	$ 29,019			$ 29,019		$ 28,537
Operating loss carryforwards, subject to expiration	8,000			8,000		8,000
Goodwill and intangible assets	21,600			21,600
Tax deferred income	600			600		500
Deferred tax liabilities, other	0			0		21,100
Regulatory assets and liabilities						100
Unrecognized tax benefits	1,400			1,400		1,400
Penalties and interest expense	100		$ 0	200	$ 200
Penalties and interest accrued	$ 1,300			$ 1,300		$ 1,100