Derivative Financial Instruments Expired Interest Rate Swap Agreements (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended							9 Months Ended
	Sep. 30, 2012 Interest Rate Swap 8 [Member]	Sep. 30, 2012 Interest Rate Swap 1 [Member]	Sep. 30, 2013 Notional Period 1 [Member] Interest Rate Swap 8 [Member]	Sep. 30, 2013 Notional Period 1 [Member] Interest Rate Swap 1 [Member]	Sep. 30, 2013 Notional Period 2 [Member] Interest Rate Swap 1 [Member]	Sep. 30, 2013 Notional Period 3 [Member] Interest Rate Swap 1 [Member]	Sep. 30, 2013 Notional Period 4 [Member] Interest Rate Swap 1 [Member]	Sep. 30, 2013 1-month LIBOR [Member] Notional Period 1 [Member] Interest Rate Swap 8 [Member]	Sep. 30, 2013 1-month LIBOR [Member] Notional Period 1 [Member] Interest Rate Swap 1 [Member]	Sep. 30, 2013 1-month LIBOR [Member] Notional Period 2 [Member] Interest Rate Swap 1 [Member]	Sep. 30, 2013 1-month LIBOR [Member] Notional Period 3 [Member] Interest Rate Swap 1 [Member]	Sep. 30, 2013 1-month LIBOR [Member] Notional Period 4 [Member] Interest Rate Swap 1 [Member]
Derivatives [Line Items]
Effective Date	Oct. 06, 2008	Oct. 04, 2012
Expiration Date	Sep. 30, 2013	Sep. 30, 2013
Notional Amount			$ 120,000	$ 1,450,000	$ 1,350,000	$ 1,300,000	$ 1,250,000
Pay Fixed Rate			3.88%	0.25%	0.25%	0.25%	0.25%
Receive Variable Rate								1-month LIBOR	1-month LIBOR	1-month LIBOR	1-month LIBOR	1-month LIBOR