Pension Plans and Other Postretirement Benefits (Details 1) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Defined Benefit Plan [Member]
Change in benefit obligation:
Accumulated postretirement benefit obligations at beginning of year	$ 39,483	$ 40,994	$ 41,736
Service cost	360	360	360
Interest cost	1,679	1,369	1,427
Plan amendments	0	0	0
Actuarial loss (gain)	1,254	624	1,686
Benefits paid	(1,737)	(1,715)	(1,664)
Settlements	(6,760)	(2,149)	(2,551)
Accumulated postretirement benefit obligations at end of year	34,279	39,483	40,994
Change in plan assets:
Fair value of plan assets at beginning of year	35,879	32,757	31,653
Actual return on plan assets	2,535	4,396	3,168
Employer contributions	2,000	3,103	2,534
Benefits paid	(1,737)	(1,715)	(1,664)
Expenses paid	(509)	(513)	(383)
Settlements	(6,760)	(2,149)	(2,551)
Fair value of plan assets at end of year	31,408	35,879	32,757
Funded status	(2,871)	(3,604)	(8,237)
Prepaid (accrued) benefit expense	10,656	12,331	11,188
Total amount recognized in Consolidated Balance Sheets, all in other liabilities	(2,871)	(3,604)	(8,237)
Amounts recognized in accumulated other comprehensive income (loss) ("AOCI"):
Prior service cost	0	0	0
Net actuarial loss	13,527	15,935	19,425
Total amount recognized in AOCI	13,527	15,935	19,425
Information for pension plans with an accumulated benefit obligation greater than plan assets:
Projected benefit obligation	34,729	39,483	40,994
Accumulated benefit obligation	34,729	39,483	40,994
Fair value of plan assets	31,408	35,879	32,757
Supplemental Defined Benefit Plans [Member]
Change in benefit obligation:
Accumulated postretirement benefit obligations at beginning of year	16,706	18,192	18,012
Service cost	0	0	0
Interest cost	716	616	676
Plan amendments	0	0	0
Actuarial loss (gain)	2,431	(783)	817
Benefits paid	(1,329)	(1,319)	(1,313)
Settlements	0	0	0
Accumulated postretirement benefit obligations at end of year	18,524	16,706	18,192
Change in plan assets:
Fair value of plan assets at beginning of year	0	0	0
Actual return on plan assets	0	0	0
Employer contributions	1,329	1,319	1,313
Benefits paid	(1,329)	(1,319)	(1,313)
Expenses paid	0	0	0
Settlements	0	0	0
Fair value of plan assets at end of year	0	0	0
Funded status	(18,524)	(16,706)	(18,192)
Prepaid (accrued) benefit expense	(12,024)	(12,479)	(12,855)
Total amount recognized in Consolidated Balance Sheets, all in other liabilities	(18,524)	(16,706)	(18,192)
Amounts recognized in accumulated other comprehensive income (loss) ("AOCI"):
Prior service cost	0	0	124
Net actuarial loss	6,500	4,227	5,213
Total amount recognized in AOCI	6,500	4,227	5,337
Information for pension plans with an accumulated benefit obligation greater than plan assets:
Projected benefit obligation	18,524	16,706	18,192
Accumulated benefit obligation	18,524	16,706	18,192
Fair value of plan assets	$ 0	$ 0	$ 0