Credit Facilities (Details) (USD $)	0 Months Ended	3 Months Ended	6 Months Ended	12 Months Ended	0 Months Ended
	Dec. 23, 2014	Dec. 31, 2014 financial_institution	Jun. 30, 2014 financial_institution	Dec. 31, 2014 financial_institution	Jun. 06, 2014	Feb. 28, 2013	Dec. 31, 2013	Nov. 11, 2014	Nov. 12, 2014	Jan. 03, 2014	Nov. 05, 2013
Line of Credit Facility [Line Items]
Outstanding Loan Amount		$ 3,759,935,000		$ 3,759,935,000			$ 1,301,114,000
Credit facilities		3,184,000,000		3,184,000,000			1,969,800,000
Line of Credit [Member] | Senior Corporate Credit Facility [Member]
Line of Credit Facility [Line Items]
Number of financial institutions		20	20	20
Credit facility, current borrowing capacity		4,650,000,000		4,650,000,000				4,650,000,000
Credit facility, maximum borrowing capacity			6,000,000,000
Credit facility, increase (decrease), net		50,000,000
Credit facility, length of extension option				1 year
Write off of unamortized (premium) discount			3,900,000
Credit facilities	3,600,000,000	3,200,000,000		3,200,000,000
Extension period for receipt of financial statements	45 days
Credit facility, undrawn commitment		416,000,000		416,000,000
Line of Credit [Member] | Senior Corporate Credit Facility [Member] | Swingline Facility [Member]
Line of Credit Facility [Line Items]
Extinguishment of debt, amount	25,000,000
Line of Credit [Member] | Senior Corporate Credit Facility [Member] | Minimum [Member]
Line of Credit Facility [Line Items]
Credit facility, commitment fee percentage				0.15%
Line of Credit [Member] | Senior Corporate Credit Facility [Member] | Maximum [Member]
Line of Credit Facility [Line Items]
Credit facility, commitment fee percentage				0.25%
Credit facility, unused capacity fee				0.25%
Line of Credit [Member] | Senior Corporate Credit Facility [Member] | Line of Credit [Member]
Line of Credit Facility [Line Items]
Outstanding Loan Amount			4,600,000,000
Line of Credit [Member] | Senior Corporate Credit Facility [Member] | Term Loan Facility [Member]
Line of Credit Facility [Line Items]
Credit facility, current borrowing capacity			1,200,000,000
Line of Credit [Member] | Senior Corporate Credit Facility [Member] | Term Loan Facility [Member] | LIBOR [Member]
Line of Credit Facility [Line Items]
Interest rate, stated percentage		1.60%		1.60%
Line of Credit [Member] | Senior Corporate Credit Facility [Member] | Term Loan Facility [Member] | Minimum [Member] | LIBOR [Member]
Line of Credit Facility [Line Items]
Basis spread on variable rate				1.15%
Line of Credit [Member] | Senior Corporate Credit Facility [Member] | Term Loan Facility [Member] | Minimum [Member] | Base Rate [Member]
Line of Credit Facility [Line Items]
Basis spread on variable rate				0.15%
Line of Credit [Member] | Senior Corporate Credit Facility [Member] | Term Loan Facility [Member] | Maximum [Member] | LIBOR [Member]
Line of Credit Facility [Line Items]
Basis spread on variable rate				2.05%
Line of Credit [Member] | Senior Corporate Credit Facility [Member] | Term Loan Facility [Member] | Maximum [Member] | Base Rate [Member]
Line of Credit Facility [Line Items]
Basis spread on variable rate				1.05%
Line of Credit [Member] | Senior Corporate Credit Facility [Member] | Term Loan Facility, Delayed Draw Component [Member]
Line of Credit Facility [Line Items]
Credit facility, current borrowing capacity			200,000,000
Line of Credit [Member] | Senior Corporate Credit Facility [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Repayments of revolving credit facility		1,200,000,000
Line of Credit [Member] | Senior Corporate Credit Facility [Member] | Revolving Credit Facility [Member] | LIBOR [Member]
Line of Credit Facility [Line Items]
Interest rate, stated percentage		1.35%		1.35%
Line of Credit [Member] | Senior Corporate Credit Facility [Member] | Revolving Credit Facility [Member] | Federal Funds Rate [Member]
Line of Credit Facility [Line Items]
Basis spread on variable rate				0.50%
Line of Credit [Member] | Senior Corporate Credit Facility [Member] | Revolving Credit Facility [Member] | Minimum [Member] | LIBOR [Member]
Line of Credit Facility [Line Items]
Basis spread on variable rate				1.00%
Line of Credit [Member] | Senior Corporate Credit Facility [Member] | Revolving Credit Facility [Member] | Minimum [Member] | Base Rate [Member]
Line of Credit Facility [Line Items]
Basis spread on variable rate				0.00%
Line of Credit [Member] | Senior Corporate Credit Facility [Member] | Revolving Credit Facility [Member] | Maximum [Member] | LIBOR [Member]
Line of Credit Facility [Line Items]
Basis spread on variable rate				1.80%
Line of Credit [Member] | Senior Corporate Credit Facility [Member] | Revolving Credit Facility [Member] | Maximum [Member] | Base Rate [Member]
Line of Credit Facility [Line Items]
Basis spread on variable rate				0.80%
Line of Credit [Member] | Senior Corporate Credit Facility [Member] | Revolving Credit Facility, Dollar Denominated [Member]
Line of Credit Facility [Line Items]
Credit facility, current borrowing capacity			3,250,000,000						4,000,000,000
Line of Credit [Member] | Senior Corporate Credit Facility [Member] | Revolving Credit Facility, Multi-Currency Denominated [Member]
Line of Credit Facility [Line Items]
Credit facility, current borrowing capacity			250,000,000
Line of Credit [Member] | Senior Corporate Credit Facility [Member] | Line of Credit, Variable Interest Rate [Member]
Line of Credit Facility [Line Items]
Interest rate, stated percentage		1.95%		1.95%
Credit facilities		2,200,000,000		2,200,000,000
Line of Credit [Member] | Senior Corporate Credit Facility [Member] | Line of Credit, Fixed Interest Rate [Member]
Line of Credit Facility [Line Items]
Credit facilities		1,000,000,000		1,000,000,000
Line of credit, amount bearing fixed interest rate, percentage		3.28%		3.28%
Line of Credit [Member] | Regions Bank Unsecured Credit Facility [Member] | ARCT IV [Member]
Line of Credit Facility [Line Items]
Credit facility, current borrowing capacity										800,000,000
Credit facilities										760,000,000
Line of Credit [Member] | Regions Bank Unsecured Credit Facility [Member] | Term Loan Facility [Member] | ARCT IV [Member]
Line of Credit Facility [Line Items]
Credit facilities										300,000,000
Line of Credit [Member] | Regions Bank Unsecured Credit Facility [Member] | Revolving Credit Facility [Member] | ARCT IV [Member]
Line of Credit Facility [Line Items]
Credit facilities										460,000,000
Line of Credit [Member] | Unsecured Credit Facility [Member] | CapLease [Member]
Line of Credit Facility [Line Items]
Credit facility, current borrowing capacity											150,000,000
Line of Credit [Member] | Unsecured Credit Facility [Member] | CapLease [Member] | Line of Credit [Member]
Line of Credit Facility [Line Items]
Extinguishment of debt, amount					150,000,000
Line of Credit [Member] | Senior Secured Revolving Credit Facility [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Effective interest rate						3.11%
Line of Credit [Member] | Senior Secured Revolving Credit Facility [Member] | Revolving Credit Facility [Member] | Line of Credit [Member]
Line of Credit Facility [Line Items]
Extinguishment of debt, amount						124,600,000