Derivative Financial Instruments Expired Interest Rate Derivative Instruments (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2014
Interest Rate Swap 8 [Member]
Derivative Fair Value [Line Items]
Effective date	Oct. 06, 2008
Expiration date	Sep. 30, 2013
Interest Rate Swap 1 [Member]
Derivative Fair Value [Line Items]
Effective date	Oct. 04, 2012
Expiration date	Sep. 30, 2013
Notional Period 1 [Member] | Interest Rate Swap 8 [Member]
Derivative Fair Value [Line Items]
Notional amount	$ 120,000
Paid fixed rate	3.88%
Notional Period 1 [Member] | Interest Rate Swap 1 [Member]
Derivative Fair Value [Line Items]
Notional amount	1,450,000
Paid fixed rate	0.25%
Notional Period 2 [Member] | Interest Rate Swap 1 [Member]
Derivative Fair Value [Line Items]
Notional amount	1,350,000
Paid fixed rate	0.25%
Notional Period 3 [Member] | Interest Rate Swap 1 [Member]
Derivative Fair Value [Line Items]
Notional amount	1,300,000
Paid fixed rate	0.25%
Notional Period 4 [Member] | Interest Rate Swap 1 [Member]
Derivative Fair Value [Line Items]
Notional amount	$ 1,250,000
Paid fixed rate	0.25%