Benefit Plans Reconciliation of Funded Status (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of assets at end of year	$ 95,353	$ 79,020
Pension Plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of year	140,999	123,904
Service cost	4,594	4,288	3,516
Interest cost	5,393	5,349	5,313
Actuarial loss	(18,082)	11,090
Benefits paid	(4,205)	(3,632)
Benefit obligation at end of year	128,699	140,999	123,904
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of assets at beginning of year	75,542	62,763
Actual return on plan assets	10,478	6,645
Employer contributions	9,543	9,766
Benefits paid	(4,205)	(3,632)
Fair value of assets at end of year	91,358	75,542	62,763
Funded status at end of year	(37,341)	(65,457)
Other Postretirement Benefit Plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of year	12,243	10,796
Service cost	361	339	273
Interest cost	508	452	467
Actuarial loss	(1,829)	994
Benefits paid	(307)	(338)
Benefit obligation at end of year	10,976	12,243	10,796
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of assets at beginning of year	3,478	2,321
Actual return on plan assets	325	838
Employer contributions	445	596
Benefits paid	(253)	(277)
Fair value of assets at end of year	3,995	3,478	2,321
Funded status at end of year	$ (6,981)	$ (8,765)