Changes in Pension and Other Postretirement Benefit Plans (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Other Postretirement Benefit Plans, Defined Benefit
Change in Projected Benefit Obligation [Abstract]
Accumulated postretirement benefit obligation at beginning of year	$ 4,379	$ 4,635
Service cost	153	161	164
Interest cost	148	170	222
Benefit payments	(201)	(193)
Actuarial (gain) loss	(2,502)	(394)
Accumulated postretirement benefit obligation at end of year	1,977	4,379	4,635
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]
Funded status – net prepaid (liability)	(1,977)	(4,379)
Pension and Other Postretirement Defined Benefit Plans, Current Liabilities	(139)	(296)
Pension and Other Postretirement Defined Benefit Plans, Liabilities, Noncurrent	(1,838)	(4,083)
Net amount recognized	(1,977)	(4,379)
Pension and Other Postretirement Benefit Plans, Accumulated Other Comprehensive Income (Loss), before Tax [Abstract]
Pension and Other Postretirement Benefit Plans, Accumulated Other Comprehensive Income (Loss), Net Gains (Losses), before Tax	3,139	661
Pension and Other Postretirement Benefit Plans, Accumulated Other Comprehensive Income (Loss), before Tax	3,139	661
Pension Plans
Change in Projected Benefit Obligation [Abstract]
Accumulated postretirement benefit obligation at beginning of year	180,551
Projected benefit obligation at beginning of year	181,137	164,407
Service cost	699	608	539
Interest cost	6,327	6,832	7,393
Benefit payments	(7,097)	(6,558)
Actuarial (gain) loss	24,077	(15,848)
Projected benefit obligation at end of year	156,989	181,137	164,407
Accumulated postretirement benefit obligation at end of year	156,474	180,551
Change in Plan Assets [Abstract]
Fair value of plan assets at beginning of year	187,150	174,938
Defined Benefit Plan, Actual (Loss) Return on Plan Assets	(11,966)	18,463
Employer contributions	321	307
Fair value of plan assets at end of year	168,408	187,150	174,938
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]
Funded status – net prepaid (liability)	11,419	6,013
Defined Benefit Plan, Assets for Plan Benefits	16,515	12,891
Accrued liabilities	(325)	(309)
Pension benefit obligations	(4,771)	(6,569)
Net amount recognized	11,419	6,013
Pension and Other Postretirement Benefit Plans, Accumulated Other Comprehensive Income (Loss), before Tax [Abstract]
Pension and Other Postretirement Benefit Plans, Accumulated Other Comprehensive Income (Loss), Net Gains (Losses), before Tax	(25,002)	(29,778)
Pension and Other Postretirement Benefit Plans, Accumulated Other Comprehensive Income (Loss), Net Prior Service Cost (Credit), before Tax	(1,295)	(1,617)
Pension and Other Postretirement Benefit Plans, Accumulated Other Comprehensive Income (Loss), before Tax	$ (26,297)	$ (31,395)