Derivative Financial Instruments Outstanding Interest Rate Swap Agreements (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013
Interest Rate Swap 2 [Member]
Derivatives [Line Items]
Effective Date	Sep. 30, 2013
Expiration Date	Sep. 30, 2014
Interest Rate Swap 2 [Member] | Notional Period 1 [Member]
Derivatives [Line Items]
Notional Amount	$ 1,350,000
Pay Fixed Rate	0.35%
Interest Rate Swap 2 [Member] | Notional Period 2 [Member]
Derivatives [Line Items]
Notional Amount	1,300,000
Pay Fixed Rate	0.35%
Interest Rate Swap 2 [Member] | Notional Period 3 [Member]
Derivatives [Line Items]
Notional Amount	1,250,000
Pay Fixed Rate	0.35%
Interest Rate Swap 2 [Member] | Notional Period 4 [Member]
Derivatives [Line Items]
Notional Amount	1,200,000
Pay Fixed Rate	0.35%
Interest Rate Swap 3 [Member]
Derivatives [Line Items]
Effective Date	Sep. 30, 2014
Expiration Date	Sep. 30, 2015
Interest Rate Swap 3 [Member] | Notional Period 1 [Member]
Derivatives [Line Items]
Notional Amount	1,150,000
Pay Fixed Rate	0.54%
Interest Rate Swap 3 [Member] | Notional Period 2 [Member]
Derivatives [Line Items]
Notional Amount	1,100,000
Pay Fixed Rate	0.54%
Interest Rate Swap 3 [Member] | Notional Period 3 [Member]
Derivatives [Line Items]
Notional Amount	1,050,000
Pay Fixed Rate	0.54%
Interest Rate Swap 3 [Member] | Notional Period 4 [Member]
Derivatives [Line Items]
Notional Amount	1,000,000
Pay Fixed Rate	0.54%
Interest Rate Swap 4 [Member]
Derivatives [Line Items]
Effective Date	Sep. 30, 2015
Expiration Date	Sep. 30, 2016
Interest Rate Swap 4 [Member] | Notional Period 1 [Member]
Derivatives [Line Items]
Notional Amount	350,000
Pay Fixed Rate	0.93%
Interest Rate Swap 5 [Member]
Derivatives [Line Items]
Effective Date	Sep. 30, 2016
Expiration Date	Sep. 30, 2026
Interest Rate Swap 5 [Member] | Notional Period 1 [Member]
Derivatives [Line Items]
Notional Amount	100,000
Pay Fixed Rate	2.79%
Interest Rate Swap 6 [Member]
Derivatives [Line Items]
Effective Date	Sep. 30, 2016
Expiration Date	Sep. 30, 2026
Interest Rate Swap 6 [Member] | Notional Period 1 [Member]
Derivatives [Line Items]
Notional Amount	100,000
Pay Fixed Rate	2.79%
Interest Rate Swap 7 [Member]
Derivatives [Line Items]
Effective Date	Sep. 30, 2016
Expiration Date	Sep. 30, 2026
Interest Rate Swap 7 [Member] | Notional Period 1 [Member]
Derivatives [Line Items]
Notional Amount	$ 100,000
Pay Fixed Rate	2.80%
1-month LIBOR [Member] | Interest Rate Swap 2 [Member] | Notional Period 1 [Member]
Derivatives [Line Items]
Receive Variable Rate	1-month LIBOR
1-month LIBOR [Member] | Interest Rate Swap 2 [Member] | Notional Period 2 [Member]
Derivatives [Line Items]
Receive Variable Rate	1-month LIBOR
1-month LIBOR [Member] | Interest Rate Swap 2 [Member] | Notional Period 3 [Member]
Derivatives [Line Items]
Receive Variable Rate	1-month LIBOR
1-month LIBOR [Member] | Interest Rate Swap 2 [Member] | Notional Period 4 [Member]
Derivatives [Line Items]
Receive Variable Rate	1-month LIBOR
1-month LIBOR [Member] | Interest Rate Swap 3 [Member] | Notional Period 1 [Member]
Derivatives [Line Items]
Receive Variable Rate	1-month LIBOR
1-month LIBOR [Member] | Interest Rate Swap 3 [Member] | Notional Period 2 [Member]
Derivatives [Line Items]
Receive Variable Rate	1-month LIBOR
1-month LIBOR [Member] | Interest Rate Swap 3 [Member] | Notional Period 3 [Member]
Derivatives [Line Items]
Receive Variable Rate	1-month LIBOR
1-month LIBOR [Member] | Interest Rate Swap 3 [Member] | Notional Period 4 [Member]
Derivatives [Line Items]
Receive Variable Rate	1-month LIBOR
1-month LIBOR [Member] | Interest Rate Swap 4 [Member] | Notional Period 1 [Member]
Derivatives [Line Items]
Receive Variable Rate	1-month LIBOR
3-month LIBOR [Member] | Interest Rate Swap 5 [Member] | Notional Period 1 [Member]
Derivatives [Line Items]
Receive Variable Rate	3-month LIBOR
3-month LIBOR [Member] | Interest Rate Swap 6 [Member] | Notional Period 1 [Member]
Derivatives [Line Items]
Receive Variable Rate	3-month LIBOR
3-month LIBOR [Member] | Interest Rate Swap 7 [Member] | Notional Period 1 [Member]
Derivatives [Line Items]
Receive Variable Rate	3-month LIBOR