Note 2 - Significant Accounting Policies and Methods of Application (Details) (USD $) Share data in Millions, unless otherwise specified	3 Months Ended												4 Months Ended	12 Months Ended							3 Months Ended		12 Months Ended			0 Months Ended		12 Months Ended		1 Months Ended			12 Months Ended												12 Months Ended						4 Months Ended	12 Months Ended								1 Months Ended			1 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2011	Dec. 31, 2013 Asset Retirement Obligation Costs [Member] Storage Facilities [Member]	Dec. 31, 2012 Asset Retirement Obligation Costs [Member] Storage Facilities [Member]	Dec. 31, 2013 Sawgrass Storage [Member] Net of Tax [Member]	Dec. 31, 2013 Sawgrass Storage [Member]	Dec. 31, 2013 Sawgrass Storage [Member]	Dec. 31, 2013 Compass Energy [Member] Net of Tax [Member]	Dec. 31, 2013 Compass Energy [Member]	Dec. 09, 2012 Nicor Gas [Member]	Dec. 09, 2011 Nicor Gas [Member]	Dec. 31, 2012 Nicor Gas [Member]	Dec. 31, 2011 Nicor Gas [Member]	Jan. 31, 2013 NiSource Inc. [Member] Customer Relationships [Member]	Jan. 31, 2013 NiSource Inc. [Member] Trade Names [Member]	Jan. 31, 2013 NiSource Inc. [Member]	Dec. 31, 2013 Goodwill [Member] Midstream Operations [Member]	Dec. 31, 2013 Wholesale Services [Member]	Dec. 31, 2012 Wholesale Services [Member]	Dec. 31, 2011 Wholesale Services [Member]	Dec. 31, 2013 Midstream Operations [Member]	Dec. 31, 2012 Midstream Operations [Member]	Dec. 31, 2011 Midstream Operations [Member]	Dec. 31, 2013 Included in Operating Expenses [Member]	Dec. 31, 2012 Included in Operating Expenses [Member]	Dec. 31, 2011 Included in Operating Expenses [Member]	Dec. 31, 2013 Tropical Shipping [Member]	Dec. 31, 2012 Tropical Shipping [Member]	Dec. 31, 2013 Atlanta Gas Light [Member]		Dec. 31, 2012 Atlanta Gas Light [Member]		Dec. 31, 2011 Atlanta Gas Light [Member]		Dec. 31, 2013 Nicor Gas [Member]	Dec. 31, 2013 Nicor Gas [Member]		Dec. 31, 2012 Nicor Gas [Member]		Dec. 31, 2011 Nicor Gas [Member]		Dec. 31, 2013 Other Current Assets [Member]	Dec. 31, 2012 Other Current Assets [Member]	Jun. 30, 2013 Customer Relationships [Member]	Jun. 30, 2013 Minimum [Member] Customer Relationships [Member]	Dec. 31, 2013 Minimum [Member]	Jun. 30, 2013 Maximum [Member] Customer Relationships [Member]	Dec. 31, 2013 Maximum [Member]
Note 2 - Significant Accounting Policies and Methods of Application (Details) [Line Items]
Investments and Cash																																											$ 80,000,000	$ 80,000,000
Customer Deposits, Current	136,000,000				143,000,000								136,000,000	136,000,000	143,000,000	143,000,000																		8,000,000
Concentration Risk, Number of Customers																																													12
LIFO Inventory Amount																																																			168,000,000	168,000,000
Inventory, Net	667,000,000				708,000,000								667,000,000	667,000,000	708,000,000	708,000,000																																			402,000,000	402,000,000
Excess of Replacement or Current Costs over Stated LIFO Value																																																			234,000,000	234,000,000
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service																																													2.60%	[1]	2.60%	[1]	2.60%	[1]	3.07%	3.10%	[2],[3]	4.10%	[2],[3]	4.10%	[2],[3]
Reduction in Depreciation Expense													19,000,000
Regulatory Liability, Noncurrent	1,518,000,000				1,477,000,000								1,518,000,000	1,518,000,000	1,477,000,000	1,477,000,000			3,000,000	3,000,000
Percent Goodwill Exceeds Carrying Value																																					5.00%																									20.00%		500.00%
Goodwill	1,888,000,000				1,837,000,000				1,813,000,000				1,888,000,000	1,888,000,000	1,837,000,000	1,837,000,000	1,813,000,000	1,813,000,000										1,423,000,000				51,000,000				2,000,000	14,000,000	14,000,000	16,000,000
Fair Value Inputs, Long-term Revenue Growth Rate																																	2.50%
Fair Value Inputs, Discount Rate																																	7.00%
Equity Method Investment, Other than Temporary Impairment																					5,000,000	8,000,000	8,000,000
Increase (Decrease) in Intangible Assets, Current														91,000,000
Amortization of Intangible Assets														14,000,000		9,000,000		0
Deferred Tax Assets, Net of Valuation Allowance, Current																																																										43,000,000	4,000,000
Deferred Tax Assets, Valuation Allowance, Current	8,000,000												8,000,000	8,000,000
Deferred Tax Liability Investments of Undistributed Foregin Earnings	31,000,000												31,000,000	31,000,000
Excise Taxes Collected														112,000,000		86,000,000		9,000,000																						110,000,000	85,000,000	9,000,000
Stock Issued During Period, Shares, Acquisitions (in Shares)																													38.2
Service Plans Acquired																																500,000
Payments to Acquire Businesses, Gross																																122,000,000
Finite-lived Intangible Assets Acquired																														46,000,000	16,000,000
Finite-Lived Intangible Asset, Useful Life																														14 years	10 years																														14 years		16 years
Customer Relationships Acquired																																																												33,000
Finite-Lived Customer Relationships, Gross																																																												32,000,000
Business Combination, Consideration Transferred																											2,500,000,000
Revenues	1,329,000,000	675,000,000	904,000,000	1,709,000,000	1,218,000,000	614,000,000	686,000,000	1,404,000,000	790,000,000	295,000,000	375,000,000	878,000,000		4,617,000,000	3,922,000,000	3,922,000,000	2,338,000,000	2,338,000,000								2,063,000,000								58,000,000	88,000,000	98,000,000	74,000,000	78,000,000	70,000,000
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	89,000,000	28,000,000	50,000,000	164,000,000	103,000,000	9,000,000	35,000,000	139,000,000	37,000,000	(4,000,000)	19,000,000	134,000,000		331,000,000		286,000,000		186,000,000										70,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment																												3,192,000,000				12,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill																												103,000,000
Proceeds from Sales of Business, Affiliate and Productive Assets														19,000,000											12,000,000
Gain (Loss) on Disposition of Business														11,000,000										5,000,000	11,000,000									11,000,000
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High																									8,000,000
Business Combination, Contingent Consideration, Asset																									3,000,000
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, Low																									$ 5,000,000
Business Combination Contingent Consideration Arrangements Earn Out Period																									5 years

[1] Average composite straight-line depreciation rates for depreciable property, excluding transportation equipment, which may be depreciated in excess of useful life and recovered in rates.

[2] Composite straight-line depreciation rates.

[3] On October 23, 2013, the Illinois Commission approved a composite depreciation rate of 3.07%. The depreciation rate was effective as of August 30, 2013, the date the depreciation study was filed, and had the effect of reducing our 2013 depreciation expense by $19 million.