Employee Benefit Plans Defined Benefit Plan (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Amounts Recognized in Accumulated Other Comprehensive Income (Loss) [Abstract]
Net amount recognized in accumulated other comprehensive loss	$ (316,985)		$ (159,178)
Qualified Pension
Fair Value of Plan Assets [Roll Forward]
Beginning balance	175,242		166,304
Actual return on plan assets	7,553		18,883
Plan settlements	(2,935)		(7,931)
Employer contributions	30,000		21,800
Benefits paid	(14,450)		(23,814)
Ending Balance	195,410		175,242		166,304
Projected Benefit Obligation [Roll Forward]
Beginning projected benefit obligation	328,776		369,841
Service cost	14,760		18,543		15,489
Interest cost	15,367		14,934		14,565
Plan settlements	(2,935)		(7,931)
Benefits paid	(14,450)		(23,814)
Actuarial loss (gain)	66,698		(42,797)
Ending projected benefit obligation	408,216		328,776		369,841
Plan assets less than projected benefit obligation	(212,806)		(153,534)
Accumulated Benefit Obligation	366,649		290,910
Amounts Recognized in the Consolidated Balance Sheets [Abstract]
Non-current liabilities	(212,806)		(153,534)
Net amount recognized	(212,806)		(153,534)
Amounts Recognized in Accumulated Other Comprehensive Income (Loss) [Abstract]
Net actuarial loss	(130,294)		(60,349)
Net amount recognized in accumulated other comprehensive loss	130,294		60,349
Post-retirement Healthcare
Fair Value of Plan Assets [Roll Forward]
Beginning balance	0		0
Employer contributions	6,097		3,704
Benefits paid	(6,097)		(3,704)
Ending Balance	0		0		0
Projected Benefit Obligation [Roll Forward]
Beginning projected benefit obligation	590,435		621,443
Service cost	24,969		26,712		25,423
Interest cost	29,908		24,555		23,958
Plan amendment	(46,277)	[1]	0	[1]
Benefits paid	(6,097)		(3,704)
Actuarial loss (gain)	148,434		(78,571)
Ending projected benefit obligation	741,372		590,435		621,443
Plan assets less than projected benefit obligation	(741,372)		(590,435)
Amounts Recognized in the Consolidated Balance Sheets [Abstract]
Current liabilities	(6,021)		(5,701)
Non-current liabilities	(735,351)		(584,734)
Net amount recognized	(741,372)		(590,435)
Defined Benefit Plan, Accumulated Other Comprehensive Income Net Prior Service Cost (Credit), after Tax	45,329		0
Prior service credit	5,782		0		0
Amounts Recognized in Accumulated Other Comprehensive Income (Loss) [Abstract]
Net actuarial loss	(253,740)		(111,960)
Net amount recognized in accumulated other comprehensive loss	208,411		111,960
Cash and cash equivalents | Qualified Pension
Fair Value of Plan Assets [Roll Forward]
Ending Balance	848		1,677
Equity securities | Qualified Pension
Fair Value of Plan Assets [Roll Forward]
Ending Balance	133,446	[2]	107,683	[2]
Fixed income securities | Qualified Pension
Fair Value of Plan Assets [Roll Forward]
Ending Balance	$ 61,116		$ 65,882

[1] In the fourth quarter of 2014, the Company amended its OPEB Plan to permit the former represented employees currently receiving post-retirement healthcare benefits to participate in that plan. Effective January 1, 2015, the former represented employees were transferred from their current plan to the OPEB Plan. The healthcare plan options available in the OPEB Plan contain higher deductibles, co-pays and co-insurance requirements than the healthcare plan options in the post-retirement healthcare plan for former represented employees. Accordingly, the Company recognized a gain as a result of the plan amendment, which will be accounted for as a prior service credit.

[2] All Level 3 equity securities are amounts held in hedged equity funds.