Debt Obligations, net (Future Scheduled Maturities) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Maturities of Long-term Debt [Abstract]
2015 (remaining nine months)	$ 105,765
2016	926,403
2017	1,272,907
2018	864,765
2019	801,936
Thereafter	300,091
Total principal maturities	4,271,867us-gaap_DebtInstrumentCarryingAmount	4,034,349us-gaap_DebtInstrumentCarryingAmount
Unamortized debt discounts, net	(10,339)	(11,665)
Total debt obligations, net	4,261,528us-gaap_LongTermDebt	4,022,684us-gaap_LongTermDebt
Unsecured Debt
Maturities of Long-term Debt [Abstract]
2015 (remaining nine months)	105,765
2016	926,403
2017	924,722
2018	600,000
2019	770,000
Thereafter	100,000
Total principal maturities	3,426,890
Unamortized debt discounts, net	(7,656)
Total debt obligations, net	3,419,234
Secured Debt
Maturities of Long-term Debt [Abstract]
2015 (remaining nine months)	0
2016	0
2017	348,185
2018	264,765
2019	31,936
Thereafter	200,091
Total principal maturities	844,977
Unamortized debt discounts, net	(2,683)
Total debt obligations, net	$ 842,294

Amount of long-term debt before deduction of unamortized discount or premium. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt, with initial maturities beyond one year or the normal operating cycle, if longer.

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The amount of debt discount (net of debt premium) that was originally recognized at the issuance of the instrument that has yet to be amortized.

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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 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 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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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 third 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 second 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 remainder of the 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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