Employee Benefit Plans (Defined Benefit Plans Disclosure) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 3,106	$ 2,699	$ 9,330	$ 8,098
Interest cost	1,341	1,314	4,028	3,943
Expected return on plan assets	(1,884)	(1,554)	(5,651)	(4,662)
Amortization of prior service cost	82	85	247	254
Amortization of prior actuarial loss	929	1,081	2,792	3,244
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	0	256	0	769
Total	3,574	3,881	10,746	11,646
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	999	465	2,271	1,907
Interest cost	680	459	1,739	1,589
Expected return on plan assets	0	0	0	0
Amortization of prior service cost	(328)	(675)	(986)	(986)
Amortization of prior actuarial loss	937	580	1,933	1,494
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	0	0	0	0
Total	$ 2,288	$ 829	$ 4,957	$ 4,004