Income Tax (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Income Tax Reconciliation, Income Tax Expense (Benefit), at Federal Statutory Income Tax Rate	$ 1,351	$ 1,429	$ 25,959	$ 20,321
Income Tax Reconciliation, Differences Regulatory Commission	65	85	1,583	1,414
Income Tax Reconciliation, Other Adjustments	(34)	(100)	(774)	(1,238)
Income Tax Expense (Benefit)	$ 1,382	$ 1,414	$ 26,768	$ 20,497
Effective Income Tax Rate	40.60%	39.20%	40.90%	40.00%