EMPLOYEE BENEFIT PLANS (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended	9 Months Ended	12 Months Ended
	Jan. 31, 2014	Dec. 31, 2015	Sep. 30, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Jan. 01, 2014
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Change in net periodic benefit cost							$ 3,400
Defined Benefit Plan Assumptions Used To Determine Benefit Obligations Rate of Compensation Increase, Minimum							3.35%	3.30%
Defined Benefit Plan Assumptions Used To Determine Benefit Obligations Rate of Compensation Increase, Maximum							3.40%	3.50%
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate							4.75%	4.25%
Expected long-term return on plan assets		7.75%	7.75%		7.75%	8.25%
Compensation increase rate - minimum		3.30%	3.30%		3.35%	3.45%
Compensation increase rate- maximum		3.50%	3.50%		3.50%	3.50%
Description of basis used to determine overall expected long-term rate of return on plan assets				We determine our overall expected long-term rate of return on plan assets, based on our review of historical returns and economic growth models. As of December 31, 2014, we updated our assumed mortality rates to incorporate the new set of mortality tables issued by the Society of Actuaries in October 2014. We determine our discount rates annually.  We estimate our discount rate based upon a comparison of the expected cash flows associated with our future payments under our defined benefit pension and other postemployment obligations to a hypothetical bond portfolio created using high-quality bonds that closely match expected cash flows.  Bond portfolios are developed by selecting a bond for each of the next 60 years based on the maturity dates of the bonds.  Bonds selected to be included in the portfolios are only those rated by Moody’s as AA- or better and exclude callable bonds, bonds with less than a minimum issue size, yield outliers and other filtering criteria to remove unsuitable bonds.
Benefit obligation									$ 1,100,000
Fair value of plan assets									$ 1,000,000
Increase in regulatory assets as a result of the transfer of unrecognized losses from ONEOK	$ 331,000
Increase in deferred income taxes as a result of the transfer of unrecognized losses from ONEOK	86,000
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Noncurrent liabilities							$ (272,309)	$ (287,779)
Defined Benefit Plan, Amount and Timing of Assets Expected to be Returned to Employer During Following 12 Month Period				0
Amortization of unrecognized prior service cost				$ (1,962)	$ (1,211)
Amortization of loss				47,494	34,169
Total recognized in other comprehensive income (loss)				$ (773)	$ 1,781	$ 0
Year that the rate reaches the ultimate trend rate							2022	2022
Defined Benefit Plan, Target Plan Asset Allocations				100.00%
Maximum [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Health care cost-trend rate assumed for next year				7.50%	7.75%
Rate to which the cost-trend rate is assumed to decline (the ultimate trend rate)				5.00%	5.00%
Minimum [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Health care cost-trend rate assumed for next year				4.00%	4.00%
Rate to which the cost-trend rate is assumed to decline (the ultimate trend rate)				4.00%	4.00%
ONEOK Profit-Sharing Plan [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Expense charged to us by ONEOK, Inc.						1,600
ONE Gas 401(k) Plan [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Percent of employee contributions matched of eligible compensation (in hundredths)				100.00%
Maximum percentage of each participants eligible compensation subject to certain limits matching (in hundredths)				6.00%
Contributions made to 401(k) plan				$ 10,200	$ 9,700
ONEOK 401(k) Plan [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Expense charged to us by ONEOK, Inc.						8,300
ONE Gas Profit-Sharing Plan [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Profit sharing contribution percentage				1.00%
Contributions made to profit-sharing plan				$ 6,500	4,000
US Large-Cap Equity [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Defined Benefit Plan, Target Plan Asset Allocations				37.40%
Investment-grade bonds [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Defined Benefit Plan, Target Plan Asset Allocations				30.00%
Developed foreign large-cap equities [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Defined Benefit Plan, Target Plan Asset Allocations				10.60%
Alternative investments [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Defined Benefit Plan, Target Plan Asset Allocations				7.70%
Mid-cap equities [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Defined Benefit Plan, Target Plan Asset Allocations				5.60%
Emerging market equities [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Defined Benefit Plan, Target Plan Asset Allocations				5.00%
Small-cap equities [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Defined Benefit Plan, Target Plan Asset Allocations				3.70%
Pension Plan [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Net periodic benefit cost				$ 37,952	$ 27,071	$ 35,000
Discount rate		4.75%	4.25%		5.25%	4.25%
Benefit obligation	863,620	$ 985,624	$ 1,028,171	1,028,171	$ 863,620	$ 863,620	$ 985,624	$ 1,028,171
Fair value of plan assets	840,699	785,161	845,396	845,396	840,699	840,699	785,161	845,396
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, beginning of period	863,620		1,028,171	1,028,171	863,620
Service cost				13,660	11,620
Plan participants' contributions				0	0
Actuarial loss				(47,607)	159,275
Benefits paid				(52,142)	(50,135)
Plan amendment				0	0
Benefit obligation, end of period		985,624		985,624	1,028,171	863,620
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period	840,699		845,396	845,396	840,699
Actual return on plan assets				(9,026)	53,907
Employer contributions				933	925
Plan participants' contributions				0	0
Fair value of plan assets, end of period		785,161		785,161	845,396	840,699
Balance at December 31							(200,463)	(182,775)
Current liabilities							(912)	(907)
Noncurrent liabilities							(199,551)	(181,868)
Balance at December 31							(200,463)	(182,775)
Accumulated benefit obligation for defined benefit pension plans							934,300	970,700
Service cost				13,660	11,620
Interest cost				43,542	43,791
Expected return on assets				(61,769)	(59,862)
Amortization of unrecognized prior service cost				266	549
Amortization of loss				42,226	30,200
Settlements				27	773
Net periodic benefit cost				37,952	27,071	35,000
Net loss arising during the period				339	(3,543)
Amortization of loss				917	518
Deferred income taxes				(483)	1,244
Total recognized in other comprehensive income (loss)				773	(1,781)
Prior service credit (cost)							0	(266)
Accumulated loss							(407,798)	(426,862)
Accumulated other comprehensive loss before regulatory assets							(407,798)	(427,128)
Regulatory asset for regulated entities							400,625	418,699
Accumulated other comprehensive loss after regulatory assets							(7,173)	(8,429)
Deferred income taxes							2,772	3,255
Accumulated other comprehensive loss, net of tax							(4,401)	(5,174)
Prior service credit (cost) expected to be recognized in following fiscal year							0
Actuarial net loss, to be recognized in 2016							35,542
Effect of a one percentage point change on total of service and interest cost - increase				263
Effect of a one percentage point change on other postemployment benefit obligation - increase				3,655
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Level 3 fair value measurement, January 1	137,044		117,791	117,791	137,044
Net realized and unrealized gains (losses)				2,246	(12,230)
Settlements				(5,600)	(7,023)
Level 3 fair value measurement, December 31		114,437		114,437	117,791	137,044
Defined Benefit Plans, Estimated Future Employer Contributions in Next Fiscal Year				900
2016							53,359
2017							54,710
2018							56,201
2019							57,238
2020							58,901
2021 through 2025							311,194
Pension Plan [Member] | Level 1 [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		414,248	443,317	443,317	443,317		414,248	443,317
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			443,317	443,317
Fair value of plan assets, end of period		414,248		414,248	443,317
Pension Plan [Member] | Level 2 [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		256,476	284,288	284,288	284,288		256,476	284,288
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			284,288	284,288
Fair value of plan assets, end of period		256,476		256,476	284,288
Pension Plan [Member] | Level 3 [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		114,437	117,791	117,791	117,791		114,437	117,791
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			$ 117,791	117,791
Fair value of plan assets, end of period		$ 114,437		114,437	117,791
Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Net periodic benefit cost				$ 5,033	$ 5,889	$ 12,300
Minimum number of years of service for certain employees to be eligible to participate in shared welfare plans that provide postemployment medical and life insurance benefits				5
Discount rate		4.75%	4.25%		5.00%	4.00%
Benefit obligation	239,171	$ 228,253	$ 257,688	$ 257,688	$ 239,171	$ 239,171	228,253	257,688
Fair value of plan assets	147,237	155,495	151,777	151,777	147,237	147,237	155,495	151,777
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, beginning of period	239,171		257,688	257,688	239,171
Service cost				3,257	3,468
Plan participants' contributions				2,915	2,642
Actuarial loss				(19,702)	14,998
Benefits paid				(14,632)	(14,196)
Plan amendment				(11,901)	0
Benefit obligation, end of period		228,253		228,253	257,688	239,171
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period	147,237		151,777	151,777	147,237
Actual return on plan assets				1,335	6,912
Employer contributions				14,100	9,182
Plan participants' contributions				2,915	2,642
Fair value of plan assets, end of period		155,495		155,495	151,777	147,237
Balance at December 31							(72,758)	(105,911)
Current liabilities							0	0
Noncurrent liabilities							(72,758)	(105,911)
Balance at December 31							(72,758)	(105,911)
Service cost				3,257	3,468
Interest cost				10,628	11,605
Expected return on assets				(11,892)	(11,393)
Amortization of unrecognized prior service cost				(2,228)	(1,760)
Amortization of loss				5,268	3,969
Net periodic benefit cost				5,033	5,889	12,300
Amortization of loss				0	0
Prior service credit (cost)							14,010	4,337
Accumulated loss							(50,447)	(64,861)
Accumulated other comprehensive loss before regulatory assets							(36,437)	(60,524)
Regulatory asset for regulated entities							36,437	60,524
Accumulated other comprehensive loss after regulatory assets							0	0
Deferred income taxes							0	0
Accumulated other comprehensive loss, net of tax							0	0
Prior service credit (cost) expected to be recognized in following fiscal year							(3,633)
Actuarial net loss, to be recognized in 2016							4,608
Effect of a one percentage point change on total of service and interest cost - decrease				(266)
Effect of a one percentage point change on other postemployment benefit obligation - decrease				(3,752)
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Defined Benefit Plans, Estimated Future Employer Contributions in Next Fiscal Year				5,800
2016							14,116
2017							13,875
2018							14,435
2019							14,956
2020							15,406
2021 through 2025							81,175
Other Postretirement Benefit Plan [Member] | Level 1 [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		54,797	50,517	50,517	50,517		54,797	50,517
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			50,517	50,517
Fair value of plan assets, end of period		54,797		54,797	50,517
Other Postretirement Benefit Plan [Member] | Level 2 [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		100,615	101,165	101,165	101,165		100,615	101,165
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			101,165	101,165
Fair value of plan assets, end of period		100,615		100,615	101,165
Other Postretirement Benefit Plan [Member] | Level 3 [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		83	95	95	95		83	95
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			95	95
Fair value of plan assets, end of period		83		83	95
Equity Securities [Member] | Pension Plan [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		468,085	505,931	505,931	505,931		468,085	505,931
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			505,931	505,931
Fair value of plan assets, end of period		468,085		468,085	505,931
Equity Securities [Member] | Pension Plan [Member] | Level 1 [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		405,935	439,165	439,165	439,165		405,935	439,165
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			439,165	439,165
Fair value of plan assets, end of period		405,935		405,935	439,165
Equity Securities [Member] | Pension Plan [Member] | Level 2 [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		62,150	66,766	66,766	66,766		62,150	66,766
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			66,766	66,766
Fair value of plan assets, end of period		62,150		62,150	66,766
Equity Securities [Member] | Pension Plan [Member] | Level 3 [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		0	0	0	0		0	0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			0	0
Fair value of plan assets, end of period		0		0	0
Equity Securities [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		62,058	62,142	62,142	62,142		62,058	62,142
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			62,142	62,142
Fair value of plan assets, end of period		62,058		62,058	62,142
Equity Securities [Member] | Other Postretirement Benefit Plan [Member] | Level 1 [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		54,560	49,553	49,553	49,553		54,560	49,553
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			49,553	49,553
Fair value of plan assets, end of period		54,560		54,560	49,553
Equity Securities [Member] | Other Postretirement Benefit Plan [Member] | Level 2 [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		7,498	12,589	12,589	12,589		7,498	12,589
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			12,589	12,589
Fair value of plan assets, end of period		7,498		7,498	12,589
Equity Securities [Member] | Other Postretirement Benefit Plan [Member] | Level 3 [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		0	0	0	0		0	0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			0	0
Fair value of plan assets, end of period		0		0	0
Cash and Money Market Funds [Member] | Pension Plan [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		15,708	20,493	20,493	20,493		15,708	20,493
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			20,493	20,493
Fair value of plan assets, end of period		15,708		15,708	20,493
Cash and Money Market Funds [Member] | Pension Plan [Member] | Level 1 [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		5,429	4,152	4,152	4,152		5,429	4,152
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			4,152	4,152
Fair value of plan assets, end of period		5,429		5,429	4,152
Cash and Money Market Funds [Member] | Pension Plan [Member] | Level 2 [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		10,279	16,341	16,341	16,341		10,279	16,341
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			16,341	16,341
Fair value of plan assets, end of period		10,279		10,279	16,341
Cash and Money Market Funds [Member] | Pension Plan [Member] | Level 3 [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		0	0	0	0		0	0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			0	0
Fair value of plan assets, end of period		0		0	0
Cash and Money Market Funds [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		13,555	6,858	6,858	6,858		13,555	6,858
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			6,858	6,858
Fair value of plan assets, end of period		13,555		13,555	6,858
Cash and Money Market Funds [Member] | Other Postretirement Benefit Plan [Member] | Level 1 [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		233	964	964	964		233	964
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			964	964
Fair value of plan assets, end of period		233		233	964
Cash and Money Market Funds [Member] | Other Postretirement Benefit Plan [Member] | Level 2 [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		13,322	5,894	5,894	5,894		13,322	5,894
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			5,894	5,894
Fair value of plan assets, end of period		13,322		13,322	5,894
Cash and Money Market Funds [Member] | Other Postretirement Benefit Plan [Member] | Level 3 [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		0	0	0	0		0	0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			0	0
Fair value of plan assets, end of period		0		0	0
Government Obligations [Member] | Pension Plan [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		44,651	47,769	47,769	47,769		44,651	47,769
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			47,769	47,769
Fair value of plan assets, end of period		44,651		44,651	47,769
Government Obligations [Member] | Pension Plan [Member] | Level 1 [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		0	0	0	0		0	0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			0	0
Fair value of plan assets, end of period		0		0	0
Government Obligations [Member] | Pension Plan [Member] | Level 2 [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		44,651	47,769	47,769	47,769		44,651	47,769
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			47,769	47,769
Fair value of plan assets, end of period		44,651		44,651	47,769
Government Obligations [Member] | Pension Plan [Member] | Level 3 [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		0	0	0	0		0	0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			0	0
Fair value of plan assets, end of period		0		0	0
Government Obligations [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		64	78	78	78		64	78
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			78	78
Fair value of plan assets, end of period		64		64	78
Government Obligations [Member] | Other Postretirement Benefit Plan [Member] | Level 1 [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		0	0	0	0		0	0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			0	0
Fair value of plan assets, end of period		0		0	0
Government Obligations [Member] | Other Postretirement Benefit Plan [Member] | Level 2 [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		64	78	78	78		64	78
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			78	78
Fair value of plan assets, end of period		64		64	78
Government Obligations [Member] | Other Postretirement Benefit Plan [Member] | Level 3 [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		0	0	0	0		0	0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			0	0
Fair value of plan assets, end of period		0		0	0
Corporate Obligations [Member] | Pension Plan [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		139,396	153,412	153,412	153,412		139,396	153,412
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			153,412	153,412
Fair value of plan assets, end of period		139,396		139,396	153,412
Corporate Obligations [Member] | Pension Plan [Member] | Level 1 [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		0	0	0	0		0	0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			0	0
Fair value of plan assets, end of period		0		0	0
Corporate Obligations [Member] | Pension Plan [Member] | Level 2 [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		139,396	153,412	153,412	153,412		139,396	153,412
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			153,412	153,412
Fair value of plan assets, end of period		139,396		139,396	153,412
Corporate Obligations [Member] | Pension Plan [Member] | Level 3 [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		0	0	0	0		0	0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			0	0
Fair value of plan assets, end of period		0		0	0
Corporate Obligations [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		200	251	251	251		200	251
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			251	251
Fair value of plan assets, end of period		200		200	251
Corporate Obligations [Member] | Other Postretirement Benefit Plan [Member] | Level 1 [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		0	0	0	0		0	0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			0	0
Fair value of plan assets, end of period		0		0	0
Corporate Obligations [Member] | Other Postretirement Benefit Plan [Member] | Level 2 [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		200	251	251	251		200	251
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			251	251
Fair value of plan assets, end of period		200		200	251
Corporate Obligations [Member] | Other Postretirement Benefit Plan [Member] | Level 3 [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		0	0	0	0		0	0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			0	0
Fair value of plan assets, end of period		0		0	0
Insurance contracts and group annuity contracts [Member] | Pension Plan [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		56,465	59,877	59,877	59,877		56,465	59,877
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			59,877	59,877
Fair value of plan assets, end of period		56,465		56,465	59,877
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Level 3 fair value measurement, January 1	63,454		59,877	59,877	63,454
Net realized and unrealized gains (losses)				2,188	3,446
Settlements				(5,600)	(7,023)
Level 3 fair value measurement, December 31		56,465		56,465	59,877	63,454
Insurance contracts and group annuity contracts [Member] | Pension Plan [Member] | Level 1 [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		0	0	0	0		0	0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			0	0
Fair value of plan assets, end of period		0		0	0
Insurance contracts and group annuity contracts [Member] | Pension Plan [Member] | Level 2 [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		0	0	0	0		0	0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			0	0
Fair value of plan assets, end of period		0		0	0
Insurance contracts and group annuity contracts [Member] | Pension Plan [Member] | Level 3 [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		56,465	59,877	59,877	59,877		56,465	59,877
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			59,877	59,877
Fair value of plan assets, end of period		56,465		56,465	59,877
Insurance contracts and group annuity contracts [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		79,531	82,353	82,353	82,353		79,531	82,353
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			82,353	82,353
Fair value of plan assets, end of period		79,531		79,531	82,353
Insurance contracts and group annuity contracts [Member] | Other Postretirement Benefit Plan [Member] | Level 1 [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		0	0	0	0		0	0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			0	0
Fair value of plan assets, end of period		0		0	0
Insurance contracts and group annuity contracts [Member] | Other Postretirement Benefit Plan [Member] | Level 2 [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		79,531	82,353	82,353	82,353		79,531	82,353
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			82,353	82,353
Fair value of plan assets, end of period		79,531		79,531	82,353
Insurance contracts and group annuity contracts [Member] | Other Postretirement Benefit Plan [Member] | Level 3 [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		0	0	0	0		0	0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			0	0
Fair value of plan assets, end of period		0		0	0
Other Investments [Member] | Pension Plan [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		60,856	57,914	57,914	57,914		60,856	57,914
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			57,914	57,914
Fair value of plan assets, end of period		60,856		60,856	57,914
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Level 3 fair value measurement, January 1	$ 73,590		57,914	57,914	73,590
Net realized and unrealized gains (losses)				58	(15,676)
Settlements				0	0
Level 3 fair value measurement, December 31		57,972		57,972	57,914	$ 73,590
Other Investments [Member] | Pension Plan [Member] | Level 1 [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		2,884	0	0	0		2,884	0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			0	0
Fair value of plan assets, end of period		2,884		2,884	0
Other Investments [Member] | Pension Plan [Member] | Level 2 [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		0	0	0	0		0	0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			0	0
Fair value of plan assets, end of period		0		0	0
Other Investments [Member] | Pension Plan [Member] | Level 3 [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		57,972	57,914	57,914	57,914		57,972	57,914
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			57,914	57,914
Fair value of plan assets, end of period		57,972		57,972	57,914
Other Investments [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		87	95	95	95		87	95
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			95	95
Fair value of plan assets, end of period		87		87	95
Other Investments [Member] | Other Postretirement Benefit Plan [Member] | Level 1 [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		4	0	0	0		4	0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			0	0
Fair value of plan assets, end of period		4		4	0
Other Investments [Member] | Other Postretirement Benefit Plan [Member] | Level 2 [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		0	0	0	0		0	0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			0	0
Fair value of plan assets, end of period		0		0	0
Other Investments [Member] | Other Postretirement Benefit Plan [Member] | Level 3 [Member]
Defined Benefit Plans and Other Postemployment Benefit Plans Table Text Block [Line Items]
Fair value of plan assets		83	95	95	95		$ 83	$ 95
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of period			$ 95	95
Fair value of plan assets, end of period		$ 83		$ 83	$ 95