Secured and Unsecured Debt (Details 5) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Aggregate maturities of unsecured debt
2014	$ 191,442
2015	242,692
2016	731,219
2017	858,099
2018	313,571
Thereafter	1,227,380
Unsecured Debt, Total	2,213,964	$ 2,221,576
Long-term Debt	3,564,403	3,583,105
Secured Debt [Member]
Aggregate maturities of unsecured debt
2014	191,363
2015	148,223
2016	274,219
2017	209,654
2018	313,571
Thereafter	213,409
Long-term Debt	1,350,439
Unsecured Debt [Member]
Aggregate maturities of unsecured debt
2014	79
2015	94,469
2016	457,000
2017	648,445
2018	0
Thereafter	1,013,971
Unsecured Debt, Total	2,213,964	$ 2,221,576
Long-term Debt	2,213,964
Fixed Rate Debt [Member] \| Secured Debt [Member]
Aggregate maturities of unsecured debt
2014	191,363
2015	148,223
2016	177,882
2017	121,685
2018	245,871
Thereafter	90,000
Long-term Debt	975,024
Variable Rate Debt [Member] \| Secured Debt [Member]
Aggregate maturities of unsecured debt
2014	0
2015	0
2016	96,337
2017	87,969
2018	67,700
Thereafter	123,409
Long-term Debt	$ 375,415

Maturities of unsecured debt.

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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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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 in the next 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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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 in the fourth 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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Including the current and noncurrent portions, carrying value as of the balance sheet date of uncollateralized debt obligations (with maturities initially due after one year or beyond the operating cycle if longer).

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