Derivatives And Risk Management Derivatives and Risk Management (Foreign Currency Exchange Contracts) (Details) CAD in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($) Caontracts	Dec. 31, 2016 CAD Caontracts	Dec. 31, 2015 USD ($) Caontracts	Dec. 31, 2015 CAD Caontracts
Schedule of Foreign Currency Derivative Contracts Outstanding [Line Items]
Number Of Days Canadian Currency Prices Are Settled With U.S. Dollars	60 days
Number of Foreign Currency Derivatives Held | Caontracts	21	21	24	24
Foreign Currency Exchange Contracts [Member] | United States of America, Dollars
Schedule of Foreign Currency Derivative Contracts Outstanding [Line Items]
Derivative, Notional Amount | $	$ 2,819		$ 1,463
Foreign Currency Exchange Contracts [Member] | Canada, Dollars
Schedule of Foreign Currency Derivative Contracts Outstanding [Line Items]
Derivative, Notional Amount | CAD		CAD 3,754		CAD 2,002