Debt Obligations, net (Secured Credit Facility Narrative) (Details) (USD $)	3 Months Ended		9 Months Ended		1 Months Ended		9 Months Ended		18 Months Ended			3 Months Ended	9 Months Ended		30 Months Ended		1 Months Ended				3 Months Ended	9 Months Ended							9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Jun. 30, 2014 February 2013 Secured Credit Facility	Feb. 28, 2013 February 2013 Secured Credit Facility	Sep. 30, 2014 February 2013 Secured Credit Facility		Jun. 10, 2014 February 2013 Secured Credit Facility	Feb. 11, 2013 February 2013 Secured Credit Facility	Oct. 15, 2012 October 2012 Secured Credit Facility	Sep. 30, 2013 2012 Tranche A-1 Facility	Sep. 30, 2014 2012 Tranche A-1 Facility	Sep. 30, 2013 2012 Tranche A-1 Facility	Sep. 30, 2014 2012 Tranche A-1 Facility	Mar. 31, 2012 2012 Tranche A-1 Facility	Mar. 31, 2012 2012 Secured Credit Facilities tranches	Mar. 31, 2012 Unsecured Notes LIBOR plus 0.50% senior convertible notes	Mar. 31, 2012 Unsecured Line of credit due June 2012	Mar. 31, 2012 Unsecured Notes 5.50% senior notes	Sep. 30, 2014 2012 Tranche A-2 Facility	Sep. 30, 2014 2012 Tranche A-2 Facility		Mar. 31, 2012 2012 Tranche A-2 Facility	Sep. 30, 2014 Unsecured Notes 4.00% Senior Notes Due November 2017	Jun. 10, 2014 Unsecured Notes 4.00% Senior Notes Due November 2017	Sep. 30, 2014 Unsecured Notes 5.00% Senior Notes Due July 2019	Jun. 10, 2014 Unsecured Notes 5.00% Senior Notes Due July 2019	Sep. 30, 2014 Minimum 2012 Tranche A-2 Facility	Sep. 30, 2014 London Interbank Offered Rate (LIBOR) Minimum February 2013 Secured Credit Facility	Sep. 30, 2014 London Interbank Offered Rate (LIBOR) Minimum 2012 Tranche A-1 Facility
Line of Credit Facility [Line Items]
Debt instrument, face amount										$ 1,710,000,000	$ 1,820,000,000					$ 410,000,000	$ 880,000,000							$ 470,000,000		$ 550,000,000		$ 770,000,000
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					22,800,000	2,700,000
Debt instrument, third party fees						3,800,000
Debt instrument, third party fees, amount recognized						3,600,000
Debt instrument, third party fees, amount capitalized						200,000
Stated interest rate																		5.50%			7.00%	7.00%			4.00%	4.00%	5.00%	5.00%
Repayment of principal amount			1,445,635,000	1,678,277,000	1,320,000,000				388,500,000						87,800,000			606,700,000	244,000,000	90,300,000
Loss on early extinguishment of debt, net	$ 186,000	$ 3,498,000	$ 24,953,000	$ 28,282,000			$ 1,100,000					$ 200,000		$ 4,400,000							$ 200,000	$ 1,000,000
Number of tranches																	2
Variable interest rate, basis							LIBOR	[1]					LIBOR									LIBOR	[2]
Percentage of par credit facilities were issued at																98.00%								98.50%
Variable interest rate, spread							3.50%	[1]					4.00%									5.75%	[2]						1.25%	1.00%	1.25%

[1] This loan had a LIBOR floor of 1.00%.

[2] The loan has a LIBOR floor of 1.25%. As of September 30, 2014, inclusive of the floor, the 2012 Tranche A-2 Facility loan incurred interest at a rate of 7.00%.