Derivative Instruments (Narrative) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012
Hedging gains or losses amortized in accumulated other comprehensive income loss	$ 1.3
Amortization period of deferred gain loss on discontinuation of cash flow hedge	1.5
Expired interest rate swaps	250
One year from balance sheet date [Member]
Hedging gains or losses amortized in accumulated other comprehensive income loss	1.2
Maximum [Member]
Credit risk of derivatives	$ 7.5