Employee Benefit Plans (Narrative) (Details)			3 Months Ended		6 Months Ended		12 Months Ended	30 Months Ended
	Feb. 22, 2015 USD ($)	Aug. 28, 2014 USD ($) employee	Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)	Aug. 22, 2017	Aug. 02, 2014 collective_bargaining_agreement
Defined Benefit Plan Disclosure [Line Items]
Actual return for qualified pension plan assets			(0.70%)	14.00%	1.90%	10.50%
Qualified Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Plan Settlement			$ (607,000)	$ 0	$ (607,000)	$ 0
Benefit obligation			369,096,000		369,096,000		$ 408,216,000
Net actuarial loss			(3,786,000)
Prior service credit			(1,726,000)
Amortization of net actuarial loss			1,886,000		$ 3,741,000
Weighted average annualized expected return on qualified pension plan assets				7.66%	7.28%
Post-retirement Healthcare Plans
Defined Benefit Plan Disclosure [Line Items]
Plan Settlement			0	$ 0	$ 0	$ 0
Benefit obligation			106,729,000		106,729,000		$ 741,372,000
Net actuarial loss			(65,550,000)
Prior service credit			(179,100,000)
Amortization of net actuarial loss			32,838,000		47,874,000
Pension Plans, Defined Benefit, Represented Employees | Qualified Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Agreements with labor unions | collective_bargaining_agreement									2
Benefit accrual rate, percent of prior rate	50.00%
Length of credited service, maximum							30 years
Maximum monthly medical reimbursement per employee		$ 800
Maximum medical reimbursement per employee spouse		$ 400
Medical insurance premiums reimbursement, maximum age of beneficiary							65 years
Number of participants | employee		290
Continuing OPEB Plan | Post-retirement Healthcare Plans
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation			91,300,000		91,300,000
Net actuarial loss					29,500,000
Prior service credit					45,300,000
Curtailment gain					5,400,000
Amortization of net actuarial loss	$ 9,800,000
Remaining gross prior service credit to be amortized			619,400,000		619,400,000
Remaining gross prior service cost to be amortized			9,800,000		9,800,000
Remaining net prior service cost to be amortized			609,600,000		$ 609,600,000
Remaining net prior service credit to be amortized, amortization period					1 year 8 months 19 days
Prior service credit recognized from plan amendment					$ 40,000,000
Continuing OPEB Plan | Post-retirement Healthcare Plans | Accumulated other comprehensive income/(loss)
Defined Benefit Plan Disclosure [Line Items]
Remaining net prior service credit to be amortized, amortization period					11 years 8 months 1 day
OPEB Plan | Post-retirement Healthcare Plans
Defined Benefit Plan Disclosure [Line Items]
Remaining unrecognized loss to be amortized			$ 192,200,000		$ 192,200,000
Remaining unrecognized loss to be amortized, amortization period					1 year 6 months
Scenario, Forecast | Pension Plans, Defined Benefit, Represented Employees | Qualified Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Retirement period for medical insurance premiums reimbursement								30 months