Fair Value Measurements and Disclosures Concentration of Risk (Details) $ in Thousands	Mar. 31, 2016 USD ($)
Concentration Risk [Line Items]
Fair Value of Derivative Assets	$ 219,125
JPMorgan Chase Bank [Member]
Concentration Risk [Line Items]
Fair Value of Derivative Assets	56,261	[1]
Canadian Imperial Bank of Commerce [Member]
Concentration Risk [Line Items]
Fair Value of Derivative Assets	63,503	[1]
Bank of Nova Scotia [Member]
Concentration Risk [Line Items]
Fair Value of Derivative Assets	41,254	[1]
Wells Fargo Bank [Member]
Concentration Risk [Line Items]
Fair Value of Derivative Assets	29,029	[1]
Natixis [Member]
Concentration Risk [Line Items]
Fair Value of Derivative Assets	24,159	[1]
Other Lenders in Our Credit Facility [Member]
Concentration Risk [Line Items]
Fair Value of Derivative Assets	$ 4,919

[1] Major lender in our revolving credit facility. See Note 7, Long-Term Debt.