Commitments and Contingencies Commitments (Details) $ in Thousands	Jan. 31, 2017 USD ($)
Unrecorded Unconditional Purchase Obligation [Line Items]
Unrecorded Unconditional Purchase Obligation	$ 31,976
Unrecorded Unconditional Purchase Obligation, Due in Next Rolling Twelve Months	31,976
Unrecorded Unconditional Purchase Obligation, Due in Rolling Year Three	0
Unrecorded Unconditional Purchase Obligation, Due within Five Years	0
Unrecorded Unconditional Purchase Obligation, Due in Rolling after Year Five	0
Postretirement Plan commitments [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Other Commitment	18,698
Other Commitment, Due in Next Twelve Months	362
Other Commitment, Due in Second and Third Year	737
Other Commitment, Due in Fourth and Fifth Year	757
Other Commitment, Due after Fifth Year	16,842
Line of Credit Commitment Fees [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Other Commitment	699	[1]
Other Commitment, Due in Next Twelve Months	212	[1]
Other Commitment, Due in Second and Third Year	424	[1]
Other Commitment, Due in Fourth and Fifth Year	63	[1]
Other Commitment, Due after Fifth Year	0	[1]
Total commitments [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Other Commitment	51,373
Other Commitment, Due in Next Twelve Months	32,550
Other Commitment, Due in Second and Third Year	1,161
Other Commitment, Due in Fourth and Fifth Year	820
Other Commitment, Due after Fifth Year	$ 16,842

[1] Amounts reflect administrative and unborrowed capacity fees under the credit facility described below.