Debt Obligations, net (Secured Credit Facility Narrative) (Details) (USD $)	12 Months Ended					12 Months Ended					12 Months Ended						1 Months Ended	12 Months Ended				1 Months Ended			1 Months Ended	12 Months Ended				1 Months Ended		12 Months Ended	1 Months Ended	12 Months Ended	1 Months Ended	12 Months Ended				1 Months Ended			12 Months Ended			12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 Secured Term Loans 5.3% and 8.2% due January 2013	Sep. 30, 2012 Secured Term Loans 5.3% and 8.2% due January 2013	Dec. 31, 2013 February 2013 Secured Credit Facility		Feb. 11, 2013 February 2013 Secured Credit Facility	Dec. 31, 2012 February 2013 Secured Credit Facility		Dec. 31, 2013 October 2012 Secured Credit Facility		Dec. 31, 2012 October 2012 Secured Credit Facility		Feb. 11, 2013 October 2012 Secured Credit Facility	Oct. 15, 2012 October 2012 Secured Credit Facility	Mar. 31, 2012 2012 Tranche A-1 Facility	Dec. 31, 2013 2012 Tranche A-1 Facility		Dec. 31, 2012 2012 Tranche A-1 Facility		Mar. 31, 2012 Secured 2011 Tranche A-2 Facility Due 2014	Mar. 31, 2011 Secured 2011 Tranche A-2 Facility Due 2014	Dec. 31, 2011 Secured 2011 Tranche A-2 Facility Due 2014	Mar. 31, 2012 2012 Tranche A-2 Facility	Dec. 31, 2013 2012 Tranche A-2 Facility		Dec. 31, 2012 2012 Tranche A-2 Facility		Mar. 31, 2012 2012 Secured Credit Facilities tranches	Mar. 31, 2012 Unsecured Notes LIBOR plus 0.50% senior convertible notes	Dec. 31, 2012 Unsecured Notes LIBOR plus 0.50% senior convertible notes	Mar. 31, 2012 Unsecured Line of credit due June 2012	Dec. 31, 2013 Unsecured Notes 5.50% senior notes	Mar. 31, 2011 2011 Secured Credit Facilities tranches	Dec. 31, 2012 2011 Secured Credit Facilities Prior to Refinancing of Debt	Dec. 31, 2011 2011 Secured Credit Facilities Prior to Refinancing of Debt	Dec. 31, 2012 2011 Secured Credit Facilities Refinancing of Debt	Oct. 31, 2012 2011 Secured Credit Facilities Refinancing of Debt	Mar. 31, 2011 Secured 2011 Tranche A-1 Facility Due 2013	Dec. 31, 2011 Secured 2011 Tranche A-1 Facility Due 2013	Feb. 11, 2013 Minimum February 2013 Secured Credit Facility	Dec. 31, 2013 Minimum 2012 Tranche A-2 Facility	Dec. 31, 2011 Minimum Secured 2011 Tranche A-1 Facility Due 2013	Feb. 11, 2013 Maximum February 2013 Secured Credit Facility	Dec. 31, 2013 Lenders from Original Credit Facility Not Participating in New Credit Facility	Dec. 31, 2013 London Interbank Offered Rate (LIBOR) Minimum February 2013 Secured Credit Facility	Dec. 31, 2013 London Interbank Offered Rate (LIBOR) Minimum October 2012 Secured Credit Facility	Dec. 31, 2013 London Interbank Offered Rate (LIBOR) Minimum 2012 Tranche A-1 Facility	Dec. 31, 2013 Net Lease Asset property	Dec. 31, 2012 Net Lease Asset Portfolio Lease Asset Sale property	Dec. 31, 2010 Net Lease Asset Portfolio Lease Asset Sale property
Line of Credit Facility [Line Items]
Debt instrument, face amount					$ 53,300,000			$ 1,706,980,000								$ 1,820,000,000
Debt instrument, covenant, minimum collateral coverage, one								125.00%
Debt instrument, covenant, minimum collateral coverage, two																																										137.50%			150.00%
Debt instrument, collateral, percent of proceeds from principal repayments and sales applied to repayment, one								100.00%
Debt instrument, collateral, percent of proceeds from principal repayments and sales applied to repayment, two								50.00%
Debt instrument, covenant, minimum collateral coverage, three								150.00%
Debt instrument, lender fees, amount						17,100,000
Debt instrument, capitalized lender fees						14,400,000
Debt instrument, lender fees, amount recorded as a loss on early extinguishment of debt						2,700,000
Debt instrument, third party fees						3,800,000							14,800,000
Debt instrument, third party fees, amount recognized						3,600,000							8,100,000
Debt instrument, third party fees, amount capitalized						200,000							6,600,000
Percentage of REIT taxable income permitted for distribution under debt covenants						100.00%
Line of credit facility, maximum amount of real estate asset distributions to stockholders						200,000,000
Repayment of principal amount	1,984,102,000	4,608,133,000	4,464,254,000			327,600,000					113,000,000							38,500,000													606,700,000	460,700,000	244,000,000	90,300,000		1,070,000,000
Long-term Debt, Gross	4,196,589,000	4,745,807,000				1,379,407,000	[1]		0	[1]	0	[2]	1,754,466,000	[2]				0	[3]	169,164,000	[3]					431,475,000	[3]	470,000,000	[3]
Gain (loss) on early extinguishment of debt, net	33,190,000	37,816,000	(101,466,000)	500,000		7,000,000					800,000		1,200,000					4,400,000		8,100,000						1,000,000										4,500,000	12,000,000	12,100,000								4,900,000
Number of real estate properties sold																																																		5	12	32
Variable interest rate, spread						3.50%	[2]				4.50%	[2]						4.00%	[3]							5.75%	[3]																1.25%	1.25%			1.00%	1.25%	1.25%
Effective interest rate						4.50%																				7.00%						5.50%
Minimum aggregate cumulative amortization payment																		41,000,000
Periods following the initial payment of amortization that additional amortization payments are due																						6 months
Borrowings from debt obligations	1,444,565,000	3,498,794,000	3,037,825,000														410,000,000						1,450,000,000		470,000,000					880,000,000					2,950,000,000					1,500,000,000
Number of tranches																														2					2
Percentage of par credit facilities were issued at																		98.00%						98.50%		98.50%															99.00%
Debt instrument, unamortized discounts and financing fees								25,600,000							30,500,000																								21,200,000
Debt instrument, deferred expense due to modification																																						$ 9,000,000

[1] This loan has a LIBOR floor of 1.00%. As of December 31, 2013, inclusive of the floor, the February 2013 Secured Credit Facility incurred interest at a rate of 4.50%.

[2] This loan has a LIBOR floor of 1.25%.

[3] These loans each have a LIBOR floor of 1.25%. As of December 31, 2013, inclusive of the floor, the 2012 Tranche A-2 Facility loan incurred interest at a rate of 7.00%.