Employee Benefits (Components of Net Periodic Benefit Cost) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income (on a pre-tax basis):
Recognized in other comprehensive income	$ 8,446	$ 10,502	$ (692)
Qualified Pension Plan [Member]
Net Periodic Benefit Cost:
Service cost	2,574	2,314	2,337
Interest cost	2,823	2,578	2,507
Expected return on plan assets	(2,985)	(2,794)	(2,541)
Amortization of prior service (credit) cost	(33)	(33)	(33)
Recognized net actuarial loss	982	392	340
Net periodic benefit cost	3,361	2,457	2,610
Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income (on a pre-tax basis):
Net loss (gain)	7,216	8,951	(1,104)
Prior service cost (credit)	33	33	33
Recognized in other comprehensive income	7,249	8,984	(1,071)
Total recognized in net periodic benefit cost and other comprehensive income	10,610	11,441	1,539
Non-Qualified Retirement Plans [Member]
Net Periodic Benefit Cost:
Service cost	150	71	93
Interest cost	503	495	515
Expected return on plan assets	0	0	0
Amortization of prior service (credit) cost	(1)	(1)	8
Recognized net actuarial loss	119	16	19
Net periodic benefit cost	771	581	635
Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income (on a pre-tax basis):
Net loss (gain)	1,195	1,517	388
Prior service cost (credit)	1	1	(8)
Recognized in other comprehensive income	1,196	1,518	380
Total recognized in net periodic benefit cost and other comprehensive income	$ 1,967	$ 2,099	$ 1,015