Derivative Financial Instruments - Summary of Underlying Notional Amounts and Aggregate Fair Values (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Derivative [Line Items]
Notional	$ 12,580,549	$ 10,461,378
Total return swap	250,594
Interest Rate Swap \| Designated as Cash Flow Hedges
Derivative [Line Items]
Notional	5,142,500	3,873,000
Fair Value	(2,230)	(5,686)
Interest Rate Swap \| Not Designated As Hedges
Derivative [Line Items]
Notional	3,237,133	3,444,459
Fair Value	(26,205)	(31,360)
Interest Rate Caps
Derivative [Line Items]
Notional	4,929,458	4,616,960
Fair Value	43,599	28,274
Options for Interest Rate Caps
Derivative [Line Items]
Notional	4,929,458	4,616,960
Fair Value	$ (43,680)	$ (28,389)

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 12

-Section 13

-Sentence Column B

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- Definition

Fair values as of the balance sheet date of the net amount of all assets and liabilities resulting from contracts that meet the criteria of being accounted for as derivative instruments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 45

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958

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- Definition

Sum of the carrying amounts as of the date of the latest financial statement presented of securities which are owned but transferred to another party to serve as collateral to partially or fully secure a debt obligation, repurchase agreement or other current or potential obligation, and for which the transferee is not permitted to sell or re-pledge them to an unrelated party.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

-SubTopic 30

-Section 50

-Paragraph 1A

-Subparagraph (b)(1)(i)

-URI http://asc.fasb.org/extlink&oid=7523297&loc=SL6224234-111729

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