Employee Benefit Plans, Financial Instruments Recorded At Fair Value On A Recurring Basis By The Plan (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan, Information about Plan Assets [Abstract]
Supplemental retirement benefits for retired executives under other retirement benefits plan	$ 2,600	$ 2,800
Expense related to other retirement benefits plan	200	300	$ 100
401(K) Plan [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Employer contribution to plan	2,700	2,500	2,800
Pension Benefits [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	116,216	107,529	$ 117,232
Pension Benefits [Member] | Recurring Basis [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	116,216	107,529
Pension Benefits [Member] | Recurring Basis [Member] | Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	65,443	62,848
Pension Benefits [Member] | Recurring Basis [Member] | Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	50,773	44,681
Pension Benefits [Member] | Recurring Basis [Member] | Cash and Cash Equivalents [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	3,500	2,513
Pension Benefits [Member] | Recurring Basis [Member] | Cash and Cash Equivalents [Member] | Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	3,500	2,513
Pension Benefits [Member] | Recurring Basis [Member] | Cash and Cash Equivalents [Member] | Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	0	0
Pension Benefits [Member] | Recurring Basis [Member] | Foreign Equity Mutual Funds [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	33,687	33,342
Pension Benefits [Member] | Recurring Basis [Member] | Foreign Equity Mutual Funds [Member] | Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	33,687	33,342
Pension Benefits [Member] | Recurring Basis [Member] | Foreign Equity Mutual Funds [Member] | Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	0	0
Pension Benefits [Member] | Recurring Basis [Member] | Equity Mutual Funds [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	28,256	26,993
Pension Benefits [Member] | Recurring Basis [Member] | Equity Mutual Funds [Member] | Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	28,256	26,993
Pension Benefits [Member] | Recurring Basis [Member] | Equity Mutual Funds [Member] | Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	0	0
Pension Benefits [Member] | Recurring Basis [Member] | US Government Bonds [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	1,283	3,410
Pension Benefits [Member] | Recurring Basis [Member] | US Government Bonds [Member] | Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	0	0
Pension Benefits [Member] | Recurring Basis [Member] | US Government Bonds [Member] | Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	1,283	3,410
Pension Benefits [Member] | Recurring Basis [Member] | Corporate Bonds [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	49,490	41,271
Pension Benefits [Member] | Recurring Basis [Member] | Corporate Bonds [Member] | Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	0	0
Pension Benefits [Member] | Recurring Basis [Member] | Corporate Bonds [Member] | Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	$ 49,490	$ 41,271