Debt - Revolving Credit Facility Narrative (Details) - Jun. 30, 2015 - Revolving Credit Facility [Member] $ in Millions	USD ($) extension
Long-Term Debt Instrument [Line Items]
Commitment Period	5 years
Borrowing capacity	$ 4,000
Line of Credit Facility, Increase (Decrease), Net	$ 1,000
Debt Instrument Maturity Date	Dec. 15, 2019
Line of Credit Facility, Number of Expiration Period Options | extension	2
Line of Credit Facility, Expiration Period Option	1 year
Long-term Debt, Gross	$ 0
Letters of Credit Outstanding, Amount	$ 15
Interest Rate In Addition To Federal Funds Rate	0.50%
Loans Receivable, Basis Spread on Variable Rate	1.00%
Debt Instrument, Covenant Description	4.0 to 1.0
Line of Credit Facility, Guarantee Event One	cross-payment default and cross acceleration with respect to indebtedness in an aggregate principal amount of $125 million or more
Line of Credit Facility, Guarantee Event Two	bankruptcy; judgments involving liability of $125 million or more that are not paid
Line of Credit Facility, Guarantee Event Three	ERISA events
Alternative Base Rate (ABR) [Member]
Long-Term Debt Instrument [Line Items]
Line of Credit Facility, Interest Rate at Period End	0.625%
London Interbank Offered Rate (LIBOR) [Member]
Long-Term Debt Instrument [Line Items]
Line of Credit Facility, Interest Rate at Period End	1.625%
Maximum [Member]
Long-Term Debt Instrument [Line Items]
Ratio of Indebtedness to Net Capital	65
Moody's, Ba3 Rating [Member] | Minimum [Member]
Long-Term Debt Instrument [Line Items]
Debt Instrument, Credit Rating	Ba3
Standard & Poor's, BB- Rating [Member] | Minimum [Member]
Long-Term Debt Instrument [Line Items]
Debt Instrument, Credit Rating	BB-