Benefit Plans Benefit Plans (Detail 9) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	$ 862,951	$ 919,782	$ 820,272
Defined Benefit Plan, Fair Value of Plan Assets excluding assets recorded at Net Asset Value	814,671	888,273
Defined Benefit Plan Fair Value of Plan Assets, including Assets recorded at Net Asset Value	862,951	919,782
Cash and Cash Equivalents
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	111,484	154,751
Company Stock
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	2,436	3,154
U.S. Equity Mutual Funds
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	27,558	33,995
International Equity Mutual Funds
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	114,436	142,177
Defined Benefit Plan Net Asset Value Assets	2,792	0
Emerging Markets Equity Mutual Funds
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	95,838	101,442
Defined Benefit Plan Net Asset Value Assets	4,889	5,950
Fixed Income Securities, Corporate and Government Bonds
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	71,644	72,334
Fixed Income Mutual Funds, Insurance Contracts
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	24,313	24,935
Fixed Income Mutual Funds, Core Bond
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	149,941	193,656
Real Estate
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	97,717	88,054
Real Asset Mutual Funds, Commodities
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	40,267	37,302
Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	38,616	0
Other Types of Investments, Global Allocation Funds
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	21,757	24,326
Other Types of Investments Insurance linked securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	18,664	12,147
Hedge Funds, Multi-strategy [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Net Asset Value Assets	40,599	25,559
Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets excluding assets recorded at Net Asset Value	642,357	694,037
Fair Value, Inputs, Level 1 [Member] | Cash and Cash Equivalents
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	111,484	154,751
Fair Value, Inputs, Level 1 [Member] | Company Stock
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	2,436	3,154
Fair Value, Inputs, Level 1 [Member] | U.S. Equity Mutual Funds
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	4,989	6,011
Fair Value, Inputs, Level 1 [Member] | International Equity Mutual Funds
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	68,544	80,836
Fair Value, Inputs, Level 1 [Member] | Emerging Markets Equity Mutual Funds
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	95,146	100,346
Fair Value, Inputs, Level 1 [Member] | Fixed Income Securities, Corporate and Government Bonds
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	71,644	72,334
Fair Value, Inputs, Level 1 [Member] | Fixed Income Mutual Funds, Insurance Contracts
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Fair Value, Inputs, Level 1 [Member] | Fixed Income Mutual Funds, Core Bond
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	95,493	136,157
Fair Value, Inputs, Level 1 [Member] | Real Estate
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	83,879	79,218
Fair Value, Inputs, Level 1 [Member] | Real Asset Mutual Funds, Commodities
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	40,267	37,302
Fair Value, Inputs, Level 1 [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	38,616	0
Fair Value, Inputs, Level 1 [Member] | Other Types of Investments, Global Allocation Funds
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	11,195	11,781
Fair Value, Inputs, Level 1 [Member] | Other Types of Investments Insurance linked securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	18,664	12,147
Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets excluding assets recorded at Net Asset Value	170,853	192,722
Fair Value, Inputs, Level 2 [Member] | Cash and Cash Equivalents
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Fair Value, Inputs, Level 2 [Member] | Company Stock
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Fair Value, Inputs, Level 2 [Member] | U.S. Equity Mutual Funds
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	22,569	27,984
Fair Value, Inputs, Level 2 [Member] | International Equity Mutual Funds
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	45,892	61,341
Fair Value, Inputs, Level 2 [Member] | Emerging Markets Equity Mutual Funds
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	692	1,096
Fair Value, Inputs, Level 2 [Member] | Fixed Income Securities, Corporate and Government Bonds
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Fair Value, Inputs, Level 2 [Member] | Fixed Income Mutual Funds, Insurance Contracts
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	22,852	23,421
Fair Value, Inputs, Level 2 [Member] | Fixed Income Mutual Funds, Core Bond
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	54,448	57,499
Fair Value, Inputs, Level 2 [Member] | Real Estate
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	13,838	8,836
Fair Value, Inputs, Level 2 [Member] | Real Asset Mutual Funds, Commodities
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Fair Value, Inputs, Level 2 [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Fair Value, Inputs, Level 2 [Member] | Other Types of Investments, Global Allocation Funds
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	10,562	12,545
Fair Value, Inputs, Level 2 [Member] | Other Types of Investments Insurance linked securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	1,461	1,514	6,894
Defined Benefit Plan, Fair Value of Plan Assets excluding assets recorded at Net Asset Value	1,461	1,514
Fair Value, Inputs, Level 3 [Member] | Cash and Cash Equivalents
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Fair Value, Inputs, Level 3 [Member] | Company Stock
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Fair Value, Inputs, Level 3 [Member] | U.S. Equity Mutual Funds
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Fair Value, Inputs, Level 3 [Member] | International Equity Mutual Funds
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Fair Value, Inputs, Level 3 [Member] | Emerging Markets Equity Mutual Funds
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Fair Value, Inputs, Level 3 [Member] | Fixed Income Securities, Corporate and Government Bonds
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Fair Value, Inputs, Level 3 [Member] | Fixed Income Mutual Funds, Insurance Contracts
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	1,461	1,514	1,300
Fair Value, Inputs, Level 3 [Member] | Fixed Income Mutual Funds, Core Bond
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Fair Value, Inputs, Level 3 [Member] | Real Estate
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Fair Value, Inputs, Level 3 [Member] | Real Asset Mutual Funds, Commodities
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0	$ 5,594
Fair Value, Inputs, Level 3 [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Fair Value, Inputs, Level 3 [Member] | Other Types of Investments, Global Allocation Funds
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Fair Value, Inputs, Level 3 [Member] | Other Types of Investments Insurance linked securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	$ 0	$ 0