Summary of Significant Accounting Policies, Deferred Project Costs (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Accounting Policies [Abstract]
Resource planning projects	$ 4.6	$ 1.4

The total amount of allowable costs capitalized during the period by the entity pertaining to Phase-In plans which were deferred on the expectation of future recovery.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 980
-SubTopic 340
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44264-110382

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 980
-SubTopic 340
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6499958&loc=d3e44213-110381

Name:	us-gaap_PhaseInPlanAmountOfCostsDeferredForRateMakingPurposes
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant