Derivative Instruments - Fair Value Measurements (Details) (Interest Rate Swap [Member], Fair Value, Measurements, Recurring [Member], USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	$ 4,740
Derivative Financial Instruments, Liabilities, Fair Value Disclosure		1,220
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	0
Derivative Financial Instruments, Liabilities, Fair Value Disclosure		0
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	4,740
Derivative Financial Instruments, Liabilities, Fair Value Disclosure		1,220
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	0
Derivative Financial Instruments, Liabilities, Fair Value Disclosure		$ 0