Pension and OPEB (Tables)

12 Months Ended

Dec. 31, 2016

Defined Contribution Pension and Other Postretirement Plans Disclosure [Abstract]

Schedule of Changes in Accumulated Postemployment Benefit Obligations [Table Text Block]

	Pension Benefits						Other Postretirement Benefits
	at December 31,						at December 31,
	2016			2015			2016			2015
Change in benefit obligation:
Benefit obligation at beginning of period	$	763,407		$	870,471		$	671,755		$	760,959
Service cost	1,927			8,653			—			—
Interest cost	25,491			32,095			24,241			27,238
Actuarial loss (gain)	46,962			(39,563		)	77,640			(9,224		)
Plan amendments	—			—			(28,164		)	(43,598		)
Plan transfer*	—			—			—			(5,242		)
Plan curtailments	—			(26,352		)	—			—
Plan settlements	(54,197		)	(51,497		)	—			—
Participant contributions	—			—			—			1,649
Benefits and other payments	(35,709		)	(30,400		)	(45,387		)	(60,027		)
Benefit obligation at end of period	$	747,881		$	763,407		$	700,085		$	671,755
Change in plan assets:
Fair value of plan assets at beginning of period	$	669,039		$	751,176		$	—		$	—
Actual return (loss) on plan assets	50,575			(9,293		)	—			—
Company contributions	2,726			9,053			45,387			58,378
Participant contributions	—			—			—			1,649
Benefits and other payments	(35,709		)	(30,400		)	(45,387		)	(60,027		)
Plan settlements	(54,197		)	(51,497		)	—			—
Fair value of plan assets at end of period	$	632,434		$	669,039		$	—		$	—
Funded status:
Current liabilities	$	(2,904	)	$	(2,772	)	$	(40,611	)	$	(40,863	)
Noncurrent liabilities	(112,543		)	(91,596		)	(659,474		)	(630,892		)
Net obligation recognized	$	(115,447	)	$	(94,368	)	$	(700,085	)	$	(671,755	)
Amounts recognized in accumulated other comprehensive income consist of:
Net actuarial loss	$	299,865		$	288,695		$	426,392		$	367,920
Prior service credit	(1,611		)	(2,201		)	(28,164		)	—
Net amount recognized (before tax effect)	$	298,254		$	286,494		$	398,228		$	367,920

Schedule of Defined Benefit Plans Disclosures [Table Text Block]

The components of net periodic benefit costs are as follows:

Schedule of Amounts in Accumulated Other Comprehensive Income (Loss) to be Recognized over Next Fiscal Year [Table Text Block]

				Other
	Pension			Postretirement
	Benefits			Benefits
Prior service credit recognition	$	(590	)	$	(2,405	)
Actuarial loss recognition	$	9,403		$	23,112

Schedule of Accumulated Benefit Obligations in Excess of Fair Value of Plan Assets [Table Text Block]

	As of December 31,
	2016		2015
Projected benefit obligation	$	747,881	$	763,407
Accumulated benefit obligation	$	745,793	$	761,124
Fair value of plan assets	$	632,434	$	669,039

Schedule of Assumptions Used [Table Text Block]

The weighted-average assumptions used to determine benefit obligations are as follows:

	Pension Benefits				Other Postretirement Benefits
	For the Year Ended				For the Year Ended
	December 31,				December 31,
	2016		2015		2016		2015
Discount rate	4.31	%	4.50	%	4.22	%	4.50	%
Rate of compensation increase	3.90	%	3.80	%	—		—

The discount rates are determined using a Company-specific yield curve model (above-mean) developed with the assistance of an external actuary. The Company-specific yield curve models (above-mean) use a subset of the expanded bond universe to determine the Company-specific discount rate. Bonds used in the yield curve are rated AA by Moody's or Standard & Poor's as of the measurement date. The yield curve models parallel the plans' projected cash flows, and the underlying cash flows of the bonds included in the models exceed the cash flows needed to satisfy the Company plans.

The weighted-average assumptions used to determine net periodic benefit costs are as follows:

	Pension Benefits at						Other Postretirement Benefits at
	December 31,						December 31,
	2016		2015		2014		2016		2015		2014
Discount rate	4.52	%	4.07	%	4.87	%	4.50	%	4.03	%	4.88	%
Expected long-term return on plan assets	7.25	%	7.75	%	7.75	%	—		—		—
Rate of compensation increase	3.80	%	3.80	%	4.21	%	—		—		—

Schedule of Health Care Cost Trend Rates [Table Text Block]

The assumed health care cost trend rates are as follows:

	At December 31,
	2016		2015		2014
Health care cost trend rate for next year	6.31	%	6.49	%	6.03	%
Rate to which the cost trend is assumed to decline (ultimate trend rate)	4.50	%	4.50	%	4.50	%
Year that the rate reaches ultimate trend rate	2038		2038		2026

Schedule of Effect of One-Percentage-Point Change in Assumed Health Care Cost Trend Rates [Table Text Block]

Assumed health care cost trend rates have a significant effect on the amounts reported for the medical plans. A one-percentage point change in assumed health care cost trend rates would have the following effects:

	1 Percentage		1 Percentage
	Point Increase		Point Decrease
Effect on total of service and interest cost components	$	3,659	$	(3,053	)
Effect on accumulated postretirement benefit obligation	$	84,381	$	(71,751	)

Schedule of Effect of Significant Unobservable Inputs, Changes in Plan Assets [Table Text Block]

Schedule of Allocation of Plan Assets [Table Text Block]

The fair values of plan assets at December 31, 2016 and 2015 by asset category are as follows:

	Fair Value Measurements at December 31, 2016								Fair Value Measurements at December 31, 2015
			Quoted								Quoted
			Prices in								Prices in
			Active								Active
			Markets for		Significant		Significant				Markets for		Significant		Significant
			Identical		Observable		Unobservable				Identical		Observable		Unobservable
			Assets		Inputs		Inputs				Assets		Inputs		Inputs
	Total		(Level 1)		(Level 2)		(Level 3)		Total		(Level 1)		(Level 2)		(Level 3)
Asset Category
Cash/Accrued Income	$	639	$	639	$	—	$	—	$	631	$	631	$	—	$	—
US Equities (a)	11		11		—		—		10		10		—		—
Mercer Common Collective Trusts (b)	631,784		—		—		—		668,398		—		—		—
Total	$	632,434	$	650	$	—	$	—	$	669,039	$	641	$	—	$	—

Schedule of Expected Benefit Payments [Table Text Block]

The following benefit payments, reflecting expected future service, are expected to be paid: