Pension Plans (Pension Plan Net Periodic Benefit Costs) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Qualified Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost for benefits earned during the year	$ 4,596	$ 14,131	$ 11,759
Interest cost on projected benefit obligation	24,488	27,514	28,835
Expected return on plan assets	(40,767)	(44,130)	(41,047)
Amortization of prior service cost	0	57	98
Recognized net loss	12,694	9,920	4,106
Net pension benefit cost	1,011	7,492	3,751
Change in net gain or loss	19,126	29,923	66,165
Amortization of prior service cost	0	(57)	(98)
Amortization of net loss	(12,694)	(9,920)	(4,106)
Total recognized in other comprehensive income (loss)	6,432	19,946	61,961
Total recognized in net periodic benefit cost and other comprehensive income (loss)	7,443	27,438	65,712
SERP
Defined Benefit Plan Disclosure [Line Items]
Service cost for benefits earned during the year	0	206	256
Interest cost on projected benefit obligation	254	318	342
Expected return on plan assets	0	0	0
Amortization of prior service cost	0	0	0
Recognized net loss	182	218	91
Net pension benefit cost	436	742	689
Change in net gain or loss	155	(155)	660
Amortization of prior service cost	0	0	0
Amortization of net loss	(182)	(218)	(91)
Total recognized in other comprehensive income (loss)	(27)	(373)	569
Total recognized in net periodic benefit cost and other comprehensive income (loss)	$ 409	$ 369	$ 1,258