Long Term Borrowings (Details) (Bank of America NA And Other Lenders [Member]) In Millions, unless otherwise specified	1 Months Ended				1 Months Ended					1 Months Ended
	Apr. 30, 2012 USD ($)	May 31, 2012 USD ($)	Apr. 30, 2012 CAD	Aug. 31, 2011 USD ($)	Apr. 30, 2012 Minimum [Member]	Apr. 30, 2012 Maximum [Member]	Apr. 30, 2012 Interest Rate Option 1 [Member]	Apr. 30, 2012 Interest Rate Option 1 [Member] Minimum [Member]	Apr. 30, 2012 Interest Rate Option 1 [Member] Maximum [Member]	Apr. 30, 2012 Interest Rate Option 2 [Member]	Apr. 30, 2012 Interest Rate Option 3 [Member]
Debt Instruments [Line Items]
Line Of Credit Amendment Date	Apr. 30, 2012
Line of Credit Facility, Increase (Decrease) In Maximum Borrowing Capacity	$ 50
Line of Credit Facility, Maximum Borrowing Capacity	670		30
Debt Instrument, Description of Variable Rate Basis							London Interbank Offered Rate (or the Canadian equivalent)			greater of the prime rate, the federal funds rate	British Bankers Association LIBOR Rate
Debt Instrument, Basis Spread on Variable Rate								1.25%	2.25%	0.50%	1.75%
Line of Credit Facility, Commitment Fee Percentage					0.15%	0.35%
Line of Credit Facility, Expiration Date	April 2017
Line of Credit Facility, Amount Outstanding		$ 348		$ 393