Employee Benefits (Obligations and Funded Status of the Plan) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018		Dec. 31, 2017	Dec. 31, 2016
Retirement Income Plan
Change in projected benefit obligation:
Benefit obligation at end of prior year		$ 361,989		$ 337,768
Service cost excluding expenses	[1]	9,086
Service cost		10,608	[2]	8,156	$ 7,705
Interest cost		12,013		12,196	12,161
Actuarial (gain) loss		(29,911)		20,829
Benefits paid		(17,681)		(16,960)
Benefit obligation at end of year		335,496		361,989	337,768
Change in plan assets:
Fair value of plan assets at end of prior year		304,389		269,766
Actual return (loss) on plan assets		(19,683)		44,283
Employer contribution		7,300		7,300
Benefits paid		(17,681)		(16,960)
Assumed expenses		(1,522)		0
Fair value of plan assets at end of year		272,803		304,389	269,766
Funded status at end of year		(62,693)		(57,600)
Other Pension Plans
Change in projected benefit obligation:
Benefit obligation at end of prior year		28,392		27,462
Service cost		480		362	296
Interest cost		865		863	878
Actuarial (gain) loss		(1,087)		2,217
Benefits paid		(1,931)		(2,512)
Benefit obligation at end of year		26,719		28,392	27,462
Change in plan assets:
Fair value of plan assets at end of prior year		0		0
Actual return (loss) on plan assets		0		0
Employer contribution		1,931		2,512
Benefits paid		(1,931)		(2,512)
Assumed expenses		0		0
Fair value of plan assets at end of year		0		0	$ 0
Funded status at end of year		$ (26,719)		$ (28,392)

[1] (a) Service cost for the Retirement Plan for 2018 excludes assumed expenses of $1,522 thousand for administrative and investment expenses paid from plan assets during the year.

[2] (a) Service cost for the Retirement Plan for 2018 includes assumed expenses of $1,522 thousand for administrative and investment expenses paid from plan assets during the year.