Pension and Other Postretirement Benefits Fair Value of Plan Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fixed Income Pension Assets	$ 6,719
Pension Plan [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Total Pension Asset Investments Net Of Receivables And Payables	252,115	$ 249,326
Plan Asset Receivable Or Payable Accrued Interest And Dividend Income	451	486
Plan Asset Receivable Or Payable Due From Broker Securities Sold	5,170	88
Total Pension Plan Asset Receivables	5,621	574
Plan Asset Receivable Or Payable Due From Broker Securities Purchased	22	562
Defined Benefit Plan, Fair Value of Plan Assets	257,714	249,338	$ 279,164
Pension Plan [Member] | Domestic Large Cap Equity Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Total Pension Asset Investments Net Of Receivables And Payables	55,496	44,528
Pension Plan [Member] | Domestic Small/Mid Cap Equity Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Total Pension Asset Investments Net Of Receivables And Payables	28,861	23,495
Pension Plan [Member] | Foreign Equity Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Total Pension Asset Investments Net Of Receivables And Payables	47,750	43,548
Pension Plan [Member] | Emerging Market Equity Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Total Pension Asset Investments Net Of Receivables And Payables	13,457	11,120
Pension Plan [Member] | Fixed Income Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Total Pension Asset Investments Net Of Receivables And Payables		0
Pension Plan [Member] | Government Or Credit Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Total Pension Asset Investments Net Of Receivables And Payables	52,915	48,456
Pension Plan [Member] | High Yield Bond Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Total Pension Asset Investments Net Of Receivables And Payables	14,072	12,298
Pension Plan [Member] | Emerging Market Debt [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Total Pension Asset Investments Net Of Receivables And Payables	8,504	7,746
Pension Plan [Member] | Real Estate Funds [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Total Pension Asset Investments Net Of Receivables And Payables	18,739	17,261
Pension Plan [Member] | Absolute Return Strategy Investment Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Total Pension Asset Investments Net Of Receivables And Payables	3,111	36,758
Pension Plan [Member] | Cash and Cash Equivalents [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Total Pension Asset Investments Net Of Receivables And Payables	2,491	4,116
Non-published Net Asset Value [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fixed Income Pension Assets	6,719
Non-published Net Asset Value [Member] | Pension Plan [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Total Pension Asset Investments Net Of Receivables And Payables	108,420	99,866
Non-published Net Asset Value [Member] | Pension Plan [Member] | Domestic Large Cap Equity Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets	5,655	0
Non-published Net Asset Value [Member] | Pension Plan [Member] | Domestic Small/Mid Cap Equity Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets	10,232	0
Non-published Net Asset Value [Member] | Pension Plan [Member] | Foreign Equity Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets	25,346	22,823
Non-published Net Asset Value [Member] | Pension Plan [Member] | Emerging Market Equity Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets	13,457	11,120
Non-published Net Asset Value [Member] | Pension Plan [Member] | Fixed Income Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets		0
Non-published Net Asset Value [Member] | Pension Plan [Member] | Government Or Credit Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets	17,960	12,800
Non-published Net Asset Value [Member] | Pension Plan [Member] | High Yield Bond Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets	14,072	12,298
Non-published Net Asset Value [Member] | Pension Plan [Member] | Emerging Market Debt [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets	8,504	0
Non-published Net Asset Value [Member] | Pension Plan [Member] | Real Estate Funds [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets	882	0
Non-published Net Asset Value [Member] | Pension Plan [Member] | Absolute Return Strategy Investment Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets	3,111	36,758
Non-published Net Asset Value [Member] | Pension Plan [Member] | Cash and Cash Equivalents [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets	2,482	4,067
Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fixed Income Pension Assets	0
Fair Value, Inputs, Level 1 [Member] | Pension Plan [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Total Pension Asset Investments Net Of Receivables And Payables	108,740	113,804
Fair Value, Inputs, Level 1 [Member] | Pension Plan [Member] | Domestic Large Cap Equity Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets	49,841	44,528
Fair Value, Inputs, Level 1 [Member] | Pension Plan [Member] | Domestic Small/Mid Cap Equity Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets	18,629	23,495
Fair Value, Inputs, Level 1 [Member] | Pension Plan [Member] | Foreign Equity Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets	22,404	20,725
Fair Value, Inputs, Level 1 [Member] | Pension Plan [Member] | Emerging Market Equity Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Fair Value, Inputs, Level 1 [Member] | Pension Plan [Member] | Fixed Income Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets		0
Fair Value, Inputs, Level 1 [Member] | Pension Plan [Member] | Government Or Credit Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Fair Value, Inputs, Level 1 [Member] | Pension Plan [Member] | High Yield Bond Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Fair Value, Inputs, Level 1 [Member] | Pension Plan [Member] | Emerging Market Debt [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets	0	7,746
Fair Value, Inputs, Level 1 [Member] | Pension Plan [Member] | Real Estate Funds [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets	17,857	17,261
Fair Value, Inputs, Level 1 [Member] | Pension Plan [Member] | Absolute Return Strategy Investment Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Fair Value, Inputs, Level 1 [Member] | Pension Plan [Member] | Cash and Cash Equivalents [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets	9	49
Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fixed Income Pension Assets	0
Fair Value, Inputs, Level 2 [Member] | Pension Plan [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Total Pension Asset Investments Net Of Receivables And Payables	34,955	35,656
Fair Value, Inputs, Level 2 [Member] | Pension Plan [Member] | Domestic Large Cap Equity Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Fair Value, Inputs, Level 2 [Member] | Pension Plan [Member] | Domestic Small/Mid Cap Equity Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Fair Value, Inputs, Level 2 [Member] | Pension Plan [Member] | Foreign Equity Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Fair Value, Inputs, Level 2 [Member] | Pension Plan [Member] | Emerging Market Equity Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Fair Value, Inputs, Level 2 [Member] | Pension Plan [Member] | Fixed Income Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets		0
Fair Value, Inputs, Level 2 [Member] | Pension Plan [Member] | Government Or Credit Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets	34,955	35,656
Fair Value, Inputs, Level 2 [Member] | Pension Plan [Member] | High Yield Bond Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Fair Value, Inputs, Level 2 [Member] | Pension Plan [Member] | Emerging Market Debt [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Fair Value, Inputs, Level 2 [Member] | Pension Plan [Member] | Real Estate Funds [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Fair Value, Inputs, Level 2 [Member] | Pension Plan [Member] | Absolute Return Strategy Investment Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Fair Value, Inputs, Level 2 [Member] | Pension Plan [Member] | Cash and Cash Equivalents [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fixed Income Pension Assets	0
Fair Value, Inputs, Level 3 [Member] | Pension Plan [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Total Pension Asset Investments Net Of Receivables And Payables	0	0
Fair Value, Inputs, Level 3 [Member] | Pension Plan [Member] | Domestic Large Cap Equity Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Fair Value, Inputs, Level 3 [Member] | Pension Plan [Member] | Domestic Small/Mid Cap Equity Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Fair Value, Inputs, Level 3 [Member] | Pension Plan [Member] | Foreign Equity Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Fair Value, Inputs, Level 3 [Member] | Pension Plan [Member] | Emerging Market Equity Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Fair Value, Inputs, Level 3 [Member] | Pension Plan [Member] | Fixed Income Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets		0
Fair Value, Inputs, Level 3 [Member] | Pension Plan [Member] | Government Or Credit Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Fair Value, Inputs, Level 3 [Member] | Pension Plan [Member] | High Yield Bond Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Fair Value, Inputs, Level 3 [Member] | Pension Plan [Member] | Emerging Market Debt [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Fair Value, Inputs, Level 3 [Member] | Pension Plan [Member] | Real Estate Funds [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Fair Value, Inputs, Level 3 [Member] | Pension Plan [Member] | Absolute Return Strategy Investment Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Fair Value, Inputs, Level 3 [Member] | Pension Plan [Member] | Cash and Cash Equivalents [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets	$ 0	$ 0