XML 51 R40.htm IDEA: XBRL DOCUMENT v3.7.0.1

Gas in Storage (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Gas in Storage [Abstract]
LIFO Inventory Amount	$ 20.6	$ 0.0

X

- Definition

Gas in Storage [Abstract]

+ References

No definition available.

+ Details

Name:	ni_GasinStorageAbstract
Namespace Prefix:	ni_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

The amount of LIFO (last in first out) inventory present at the reporting date when inventory is also valued using different valuation methods.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6361739&loc=d3e7789-107766

+ Details

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