Fair Value Measurements and Disclosures Concentration of Risk (Details) $ in Thousands	Sep. 30, 2016 USD ($)
Concentration Risk [Line Items]
Fair Value of Derivative Assets	$ 74,027
Canadian Imperial Bank of Commerce [Member]
Concentration Risk [Line Items]
Fair Value of Derivative Assets	21,343	[1]
JPMorgan Chase Bank [Member]
Concentration Risk [Line Items]
Fair Value of Derivative Assets	17,929	[1]
Bank of Nova Scotia [Member]
Concentration Risk [Line Items]
Fair Value of Derivative Assets	15,166	[1]
Wells Fargo Bank [Member]
Concentration Risk [Line Items]
Fair Value of Derivative Assets	9,891	[1]
Natixis [Member]
Concentration Risk [Line Items]
Fair Value of Derivative Assets	7,171	[1]
Other Lenders in Our Credit Facility [Member]
Concentration Risk [Line Items]
Fair Value of Derivative Assets	2,491
Various [Member]
Concentration Risk [Line Items]
Fair Value of Derivative Assets	$ 36	[2]

[1] Major lender in our revolving credit facility. See Note 8, Long-Term Debt.

[2] Represents a total of two counterparties.