Debt - Revolving Credit Facility (Details)	Jun. 30, 2016 USD ($)	Feb. 29, 2016 USD ($)	Nov. 01, 2015 USD ($)	Jun. 30, 2015 USD ($)
Line of Credit Facility [Line Items]
Line of Credit Facility, maximum borrowing capacity	$ 3,300,000,000	$ 3,000,000,000
Line of Credit Facility, increase in borrowing capacity	$ 300,000,000
Ratio of indebtedness to net capital	0.28
Maximum [Member]
Line of Credit Facility [Line Items]
Ratio of indebtedness to net capital	0.65
Unsecured Debt [Member]
Line of Credit Facility [Line Items]
Principal amount				$ 2,000,000,000
Senior Notes 0.90% [Member]
Line of Credit Facility [Line Items]
Principal amount			$ 1,000,000,000
Interest rate			0.90%