Pension Plans (Pension Plan Net Periodic Benefit Costs) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Qualified Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost for benefits earned during the year	$ 14,131	$ 11,759	$ 14,347
Interest cost on projected benefit obligation	27,514	28,835	25,596
Expected return on plan assets	(44,130)	(41,047)	(41,347)
Amortization of prior service cost (credit)	57	98	98
Recognized net loss	9,920	4,106	9,291
Additional amount recognized due to curtailment/settlement	0	0	0
Net pension benefit cost	7,492	3,751	7,985
Change in prior service cost	0	0	0
Change in net gain or loss	29,923	66,165	(51,465)
Amortization of prior service cost (credit)	(57)	(98)	(98)
Amortization of net gain (loss)	(9,920)	(4,106)	(9,291)
Total recognized in other comprehensive income (loss)	19,946	61,961	(60,854)
Total recognized in net periodic benefit cost and other comprehensive income (loss)	27,438	65,712	(52,869)
Supplemental Employee Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost for benefits earned during the year	206	256	340
Interest cost on projected benefit obligation	318	342	311
Expected return on plan assets	0	0	0
Amortization of prior service cost (credit)	0	0	0
Recognized net loss	218	91	261
Additional amount recognized due to curtailment/settlement	0	0	276
Net pension benefit cost	742	689	1,188
Change in prior service cost	0	0	0
Change in net gain or loss	(155)	660	(1,052)
Amortization of prior service cost (credit)	0	0	0
Amortization of net gain (loss)	(218)	(91)	(261)
Total recognized in other comprehensive income (loss)	(373)	569	(1,313)
Total recognized in net periodic benefit cost and other comprehensive income (loss)	$ 369	$ 1,258	$ (125)