Employee Benefit Plans (Defined Benefit Plans Disclosure) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2,699	$ 2,479	$ 8,098	$ 7,437
Interest cost	1,314	1,168	3,943	3,503
Expected return on plan assets	(1,554)	(1,285)	(4,662)	(3,854)
Amortization of prior service cost	85	76	254	229
Amortization of prior actuarial loss	1,081	1,040	3,244	3,121
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	256	0	769	0
Total	3,881	3,478	11,646	10,436
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	465	131	1,907	2,162
Interest cost	459	408	1,589	1,694
Expected return on plan assets	0	0	0	0
Amortization of prior service cost	(675)	(467)	(986)	(467)
Amortization of prior actuarial loss	580	137	1,494	1,370
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	0	0	0	0
Total	$ 829	$ 209	$ 4,004	$ 4,759