Secured and Unsecured Debt (Details 5) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Aggregate maturities of unsecured debt
2014	$ 37,835
2015	521,233
2016	250,188
2017	402,955
2018	874,982
Thereafter	1,540,999
Unsecured Debt, Total	2,228,820	2,081,626
Long-term Debt	3,628,192	3,523,703
Secured Debt [Member]
Aggregate maturities of unsecured debt
2014	37,835
2015	197,359
2016	167,771
2017	242,955
2018	226,472
Thereafter	526,980
Long-term Debt	1,399,372
Unsecured Debt [Member]
Aggregate maturities of unsecured debt
2014	0
2015	323,874
2016	82,417
2017	160,000
2018	648,510
Thereafter	1,014,019
Unsecured Debt, Total	2,228,820	2,081,626
Long-term Debt	2,228,820
Fixed Rate Debt [Member] \| Secured Debt [Member]
Aggregate maturities of unsecured debt
2014	37,835
2015	197,359
2016	136,434
2017	177,955
2018	176,472
Thereafter	335,871
Long-term Debt	1,061,926
Variable Rate Debt [Member] \| Secured Debt [Member]
Aggregate maturities of unsecured debt
2014	0
2015	0
2016	31,337
2017	65,000
2018	50,000
Thereafter	191,109
Long-term Debt	$ 337,446

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Carrying amount of long-term debt, net of unamortized discount or premium, including current and noncurrent amounts. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing after the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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