Debt Obligations, net (Debt Obligations Summary) (Details) (USD $)					6 Months Ended			6 Months Ended			6 Months Ended			6 Months Ended			6 Months Ended				6 Months Ended						3 Months Ended			6 Months Ended																							6 Months Ended
	Jun. 30, 2012		Dec. 31, 2011		Jun. 30, 2012 Secured 2011 Tranche A-1 Facility Due 2013		Dec. 31, 2011 Secured 2011 Tranche A-1 Facility Due 2013	Jun. 30, 2012 Secured 2011 Tranche A-2 Facility Due 2014		Dec. 31, 2011 Secured 2011 Tranche A-2 Facility Due 2014	Jun. 30, 2012 Secured 2012 Tranche A-1 Facility Due 2016		Dec. 31, 2011 Secured 2012 Tranche A-1 Facility Due 2016	Jun. 30, 2012 Secured 2012 Tranche A-2 Facility Due 2017		Dec. 31, 2011 Secured 2012 Tranche A-2 Facility Due 2017	Jun. 30, 2012 Secured Term Loans Collateralized by net lease assets due through 2026	Dec. 31, 2011 Secured Term Loans Collateralized by net lease assets due through 2026	Jun. 30, 2012 Secured Credit Facility	Dec. 31, 2011 Secured Credit Facility	Jun. 30, 2012 Unsecured Line of credit due June 2012	Dec. 31, 2011 Unsecured Line of credit due June 2012	Jun. 30, 2012 Unsecured Notes 5.15% senior notes	Dec. 31, 2011 Unsecured Notes 5.15% senior notes	Jun. 30, 2012 Unsecured Notes 5.50% senior notes	Dec. 31, 2011 Unsecured Notes 5.50% senior notes	Jun. 30, 2012 Unsecured Notes LIBOR plus 0.50% senior convertible notes		Jun. 30, 2011 Unsecured Notes LIBOR plus 0.50% senior convertible notes	Jun. 30, 2012 Unsecured Notes LIBOR plus 0.50% senior convertible notes		Jun. 30, 2011 Unsecured Notes LIBOR plus 0.50% senior convertible notes	Dec. 31, 2011 Unsecured Notes LIBOR plus 0.50% senior convertible notes		Jun. 30, 2012 Unsecured Notes 8.625% senior notes	Dec. 31, 2011 Unsecured Notes 8.625% senior notes	Jun. 30, 2012 Unsecured Notes 5.95% senior notes	Dec. 31, 2011 Unsecured Notes 5.95% senior notes	Jun. 30, 2012 Unsecured Notes 6.5% senior notes	Dec. 31, 2011 Unsecured Notes 6.5% senior notes	Jun. 30, 2012 Unsecured Notes 5.70% senior notes	Dec. 31, 2011 Unsecured Notes 5.70% senior notes	Jun. 30, 2012 Unsecured Notes 6.05% senior notes	Dec. 31, 2011 Unsecured Notes 6.05% senior notes	Jun. 30, 2012 Unsecured Notes 5.875% senior notes	Dec. 31, 2011 Unsecured Notes 5.875% senior notes	Jun. 30, 2012 Unsecured Notes 5.85% senior notes	Dec. 31, 2011 Unsecured Notes 5.85% senior notes	Jun. 30, 2012 Unsecured Notes 9.0% senior notes	Dec. 31, 2011 Unsecured Notes 9.0% senior notes	Jun. 30, 2012 Unsecured Notes	Dec. 31, 2011 Unsecured Notes	Jun. 30, 2012 Other debt obligations due in October, 2035	Dec. 31, 2011 Other debt obligations due in October, 2035	Mar. 31, 2011 Minimum Secured 2011 Tranche A-1 Facility Due 2013	Mar. 31, 2011 Minimum Secured 2011 Tranche A-2 Facility Due 2014	Mar. 31, 2011 Minimum Secured 2012 Tranche A-1 Facility Due 2016	Jun. 30, 2012 Minimum Secured 2012 Tranche A-2 Facility Due 2017
Debt Instrument [Line Items]
Total debt obligations	$ 5,661,964,000	[1]	$ 5,874,183,000		$ 646,068,000		$ 961,580,000	$ 1,450,000,000		$ 1,450,000,000	$ 328,605,000		$ 0	$ 470,000,000		$ 0	$ 238,425,000	$ 293,192,000	$ 3,133,098,000	$ 2,704,772,000	$ 0	$ 243,650,000	$ 0	$ 263,466,000	$ 0	$ 92,845,000	$ 469,166,000	[2]		$ 469,166,000	[2]		$ 784,750,000	[2]	$ 501,701,000	$ 501,701,000	$ 448,453,000	$ 448,453,000	$ 67,055,000	$ 67,055,000	$ 200,601,000	$ 200,601,000	$ 105,765,000	$ 105,765,000	$ 261,403,000	$ 261,403,000	$ 99,722,000	$ 99,722,000	$ 275,000,000	$ 0	$ 2,428,866,000	$ 2,825,761,000	$ 100,000,000	$ 100,000,000
Stated interest rate (as a percent)																							5.15%		5.50%										8.625%		5.95%		6.50%		5.70%		6.05%		5.875%		5.85%		9.00%
Variable interest rate, spread (as a percent)					3.75%	[3]		5.75%	[3]		4.00%	[4]		5.75%	[4]						0.85%						0.50%	[2]		0.50%	[2]																						1.50%		1.25%	1.25%	1.25%	1.25%
Variable interest rate, basis					LIBOR	[3]		LIBOR	[3]		LIBOR	[4]		LIBOR	[4]						LIBOR									LIBOR	[2]																						LIBOR
Effective interest rate (as a percent)					5.00%			7.00%			5.25%			7.00%									5.15%				5.50%			5.50%
Stated interest rate, minimum (as a percent)																	5.05%
Stated interest rate, maximum (as a percent)																	7.68%
Debt discounts, net	(58,025,000)	[1],[2]	(36,643,000)	[2]																							2,500,000			2,500,000
Total debt obligations, net	5,603,939,000	[1]	5,837,540,000																								466,700,000			466,700,000
Number of shares per $1000 of principal amount of convertible notes																														22.2
Principal amount used for debt instrument conversion ratio																											1,000			1,000
Conversion price (in dollars per share)																											$ 45.05			$ 45.05
Carrying value of the additional paid-in-capital, or equity component of the convertible notes																											34,700,000			34,700,000
Interest expense on the convertible notes recognized																											3,100,000		4,500,000	8,300,000		8,900,000
Amortization of the debt discount																											$ 1,800,000		$ 2,900,000	$ 4,800,000		$ 5,700,000

[1] All of the Company's non-accrual loans are considered impaired and included in the table above. In addition, as of June 30, 2012 and December 31, 2011, certain loans modified through troubled debt restructurings with a recorded investment of $205.5 million and $255.3 million, respectively, are also included as impaired loans in accordance with GAAP although they are performing and on accrual status.

[2] The Company's convertible senior floating rate notes due October 2012 ("Convertible Notes") are convertible at the option of the holders into 22.2 shares per $1,000 principal amount of Convertible Notes (reflecting a conversion price of $45.05), on or after August 15, 2012, or prior to that date if certain conditions are met. None of the conversion conditions have been met as of June 30, 2012. As of June 30, 2012, the unamortized discount on these notes was $2.5 million, the net carrying amount of the liability was $466.7 million and the carrying value of the additional paid-in-capital, or equity component of the convertible notes was $34.7 million. For the three and six months ended June 30, 2012, the Company recognized interest expense on the convertible notes of $3.1 million and $8.3 million, respectively, of which $1.8 million and $4.8 million, respectively, related to the amortization of the debt discount. For the three and six months ended June 30, 2011, the Company recognized interest expense on the convertible notes of $4.5 million and $8.9 million respectively, of which $2.9 million and $5.7 million, respectively, related to the amortization of the debt discount.

[3] These loans each have a LIBOR floor of 1.25%. As of June 30, 2012, inclusive of the floors, the 2011 Tranche A-1 Facility and 2011 Tranche A-2 Facility loans incurred interest at a rate of 5.00% and 7.00%, respectively.

[4] These loans each have a LIBOR floor of 1.25%. As of June 30, 2012, inclusive of the floors, the 2012 Tranche A-1 Facility and 2012 Tranche A-2 Facility loans incurred interest at a rate of 5.25% and 7.00% respectively.