Retirement Plans (Changes in the Projected Benefit Obligation and Plan Assets) (Details) (USD $) In Thousands, unless otherwise specified	1 Months Ended	12 Months Ended
	Jan. 31, 2012	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Pension Plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of year	$ 100,216	$ 100,216	$ 86,704
Service cost		1,168	1,133	1,228
Interest cost		4,795	4,779	4,785
Net actuarial (gain) loss		13,200	11,082
Benefits paid		(4,202)	(3,482)
Benefit obligation at end of year		115,177	100,216	86,704
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	82,521	82,521	86,741
Actual return on plan assets		7,868	(738)
Employer contributions	12,000	12,000	0
Benefits paid		(4,202)	(3,482)
Fair value of plan assets at end of year		98,187	82,521	86,741
Funded (unfunded) projected benefit obligation at end of year		16,990	17,695
Accumulated benefit obligation		108,078	94,089
Postretirement Plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of year	3,290	3,290	3,757
Service cost		0	0	0
Interest cost		146	167	217
Net actuarial (gain) loss		25	(490)
Benefits paid		(218)	(144)
Benefit obligation at end of year		3,243	3,290	3,757
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	0	0	0
Actual return on plan assets		0	0
Employer contributions		218	144
Benefits paid		(218)	(144)
Fair value of plan assets at end of year		0	0	0
Funded (unfunded) projected benefit obligation at end of year		3,243	3,290
Accumulated benefit obligation		$ 3,243	$ 3,290