Qualified Employee Benefit Plans - The Retirement Plan's Asset Allocation Percentages (Details) - Retirement Plan [Member]	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, actual plan asset allocations, percent	100.00%	100.00%
Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, actual plan asset allocations, percent	61.00%	56.00%
Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, actual plan asset allocations, percent	18.00%	24.00%
Other [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, actual plan asset allocations, percent	21.00%	20.00%