Other Comprehensive Income (Loss) (Details 2) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2016
Sep. 30, 2015
Sep. 30, 2016
Sep. 30, 2015
Gain on sale of available-for-sale securities $ 455 $ 92 $ 926 $ 1,105
Pension and other employee benefits 5,218 5,368 15,435 10,843
Tax (expense) benefit (7,219) (7,115) (21,208) (22,405)
Net of tax 14,897 14,530 43,713 44,665
Reclassification out of Accumulated Other Comprehensive Income [Member] | Available for Sale Securities [Member]        
Gain on sale of available-for-sale securities [1] 455 92 926 1,105
Tax (expense) benefit [1] (182) (37) (370) (442)
Net of tax [1] 273 55 556 663
Reclassification out of Accumulated Other Comprehensive Income [Member] | Employee Benefit Plans [Member]        
Pension and other employee benefits [1],[2] (335) (201) (1,004) (1,663)
Amortization, Total before tax [1] (355) (221) (1,062) (1,312)
Tax (expense) benefit [1] 142 88 425 523
Net of tax [1] (213) (133) (637) (789)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Employee Benefit Plans Service Costs [Member]        
Pension and other employee benefits [2] $ (20) $ (20) $ (58) $ 351
[1] Amounts in parentheses indicated debits in income statement.
[2] The accumulated other comprehensive (loss) income components are included in the computation of net periodic benefit cost (See Note 10 - "Employee Benefit Plan").