Employee Benefit Plans Defined Benefit Plan - Weighted Average Assumptions Used in Calculating Benefit Obligation (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Impact of Medicare Drug Act of 2003 Subsidy on Post-Retirement Healthcare Benefits [Abstract]
Change in projected benefit obligation	(35,554)
Defined Benefit Plan, Change in Net Periodic Benefit Cost [Abstract]
Service cost	(1,356)
Interest cost	(1,641)
Amortization of loss	(2,149)
Total change in net periodic cost	(5,146)
Qualified Pension
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Discount rate	4.04%		4.92%
Rate of future increases in compensation	3.00%	[1]	3.00%	[1]
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate	4.92%		4.08%		4.63%
Expected return on plan assets	7.66%	[2]	7.54%	[2]	7.52%	[2]
Rate of compensation increase	3.00%	[1]	3.00%	[1]	3.00%	[1]
Post-retirement Healthcare
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Discount rate	4.14%		4.98%
Rate of future increases in compensation	4.00%	[1]	4.00%	[1]
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate	4.98%		4.20%		4.66%
Rate of compensation increase	4.00%	[1]	4.00%	[1]	4.00%	[1]
Rate that the cost trend rates	4.50%		4.50%		4.50%
Year that the rates reach the terminal rate	2030		2030		2030
Effect of One Percentage Point Increase in Assumed Health Care Cost Trend Rates [Abstract]
Effect on total service cost and interest cost components	14,152
Effect on benefit obligation	182,080
Effect of One Percentage Point Decrease in Assumed Health Care Cost Trend Rates [Abstract]
Effect on total service cost and interest cost components	(10,719)
Effect on benefit obligation	(138,046)
Parctipants under 65 next year | Post-retirement Healthcare
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Healthcare cost trend rate assumed for participants, next year	7.90%		8.10%		8.40%
Participants over 65 next year | Post-retirement Healthcare
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Healthcare cost trend rate assumed for participants, next year	7.90%		8.10%		8.40%

[1] The rate of future increases in compensation assumption only applies to the plans for represented employees as plans for non-represented employees are frozen.

[2] The expected return on plan assets is the long-term rate-of-return the Company expects to earn on the plan assets. In developing the expected return on plan asset assumption, the Company evaluated historical investment performance, the plans' asset allocation strategies and return forecasts for each asset class and input from its advisors. Projected returns by such advisors were based on broad equity and fixed income indices. The expected return on plan assets is reviewed annually in conjunction with other plan assumptions and, if considered necessary, revised to reflect changes in the financial markets and the investment strategy. The investment strategy and target allocations of the qualified pension plans previously disclosed in "—Plan Assets, Obligations and Funded Status—Qualified Pension Plan Assets" herein were utilized.