Income Taxes Other tax disclosures (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Taxes [Abstract]
Effective Income Tax Rate Reconciliation, Disposition of Asset, Amount		$ 1,800
Investment Tax Credit	$ 14,077	13,542	$ 12,209
Liability for Uncertain Tax Positions, Noncurrent	$ 0	$ 100