Derivative Instruments (Details)	Mar. 31, 2014 Derivative [Member] CAD	Mar. 31, 2014 Derivative [Member] GBP (£)	Dec. 31, 2013 Derivative [Member] CAD	Dec. 31, 2013 Derivative [Member] GBP (£)	Mar. 31, 2014 Financial Instruments [Member] CAD	Mar. 31, 2014 Financial Instruments [Member] GBP (£)	Dec. 31, 2013 Financial Instruments [Member] CAD	Dec. 31, 2013 Financial Instruments [Member] GBP (£)	Mar. 31, 2014 Cash Flow Hedging [Member] USD ($)	Dec. 31, 2013 Cash Flow Hedging [Member] USD ($)
Derivative [Line Items]
Derivative notional amount	600,000,000	£ 350,000,000	600,000,000	£ 350,000,000	250,000,000	£ 550,000,000	250,000,000	£ 550,000,000	$ 57,000,000	$ 57,000,000