Committed Lines of Credit (Tables)

12 Months Ended

Dec. 31, 2015

Short-term Debt [Abstract]

Schedule of Line of Credit Facilities [Table Text Block]

	2015			2014
Balance outstanding at end of period	$	105,000		$	105,000
Letters of credit outstanding at end of period	$	44,595		$	32,579
Average interest rate at end of period	1.18		%	0.93		%