Debt (Tables)	6 Months Ended
Jun. 30, 2017
Debt Instrument [Line Items]
Schedule of Debt [Table Text Block]	BT Long-term Debt consisted of the following:

Tabular disclosure of information pertaining to short-term and long-debt instruments or arrangements, including but not limited to identification of terms, features, collateral requirements and other information necessary to a fair presentation.

No definition available.

Name:	us-gaap_ScheduleOfDebtTableTextBlock
Namespace Prefix:	us-gaap_
Data Type:	nonnum:textBlockItemType
Balance Type:	na
Period Type:	duration