Retirement Plan (Changes in Benefit Obligation and Plan Assets) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Defined Benefit Pension Plans
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Pension plan's benefit obligation - beginning of year	$ 95,485	$ 95,485	$ 93,378	$ 94,083
Service cost		679	5,070
Interest cost		3,962	5,125
Amendments	(15,600)
Benefits paid		(1,379)	(1,347)
Actuarial loss		13,203	16,108
Settlements paid		(7,256)	(10,510)
Curtailment		(7,102)	(15,151)
Pension plan's benefit obligation - end of year	95,485	95,485	93,378	94,083
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets - beginning of year	77,757	77,757	61,398	64,490
Actual return on plan assets		2,615	(1,235)
Benefits paid		(1,379)	(1,347)
Employer contributions		22,379	10,000
Settlements paid		(7,256)	(10,510)
Fair value of plan assets - end of year	77,757	77,757	61,398	64,490
Under-funded balance	(17,728)	(17,728)	(31,980)
Accrued liability	(17,728)	(17,728)	(31,980)
Cumulative actuarial loss	(37,589)	(37,589)	(35,094)
Prior service cost	0	0	(966)
Total	(37,589)	(37,589)	(36,060)
Other Postretirement Benefit Plans, Defined Benefit
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Pension plan's benefit obligation - beginning of year	26,797	26,797	77,303	7,862
Service cost		1,892	1,569
Interest cost		3,519	2,193
Participant contributions		760	460
Amendments		(49,399)	(5,387)
Benefits paid		(1,275)	(1,105)
Plan combinations		0	62,632
Actuarial loss		(6,003)	9,079
Pension plan's benefit obligation - end of year	26,797	26,797	77,303	7,862
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets - beginning of year	0	0	0	0
Benefits paid		(1,275)	(1,105)
Employer contributions		515	645
Fair value of plan assets - end of year	0	0	0	0
Under-funded balance	(26,797)	(26,797)	(77,303)
Accrued liability	(26,797)	(26,797)	(77,303)
Cumulative actuarial loss	5,359	5,359	11,631
Transition obligation	0	0	0
Prior service cost	(52,174)	(52,174)	(4,997)
Total	$ (46,815)	$ (46,815)	$ 6,634