Subsequent Event (Details) $ in Millions	Oct. 15, 2015 USD ($)
Revolving credit facility, due 2020 [Member]
Subsequent Event [Line Items]
Line of Credit Facility, Current Borrowing Capacity	$ 300.0
Line of Credit Facility, Additional Borrowing Capacity	100.0
Line of Credit Facility Capacity Available for Swing-Line Loans	30.0
Line of Credit Facility Capacity Available for Letters of Credit	30.0
Revolving credit facility, due 2017 [Member]
Subsequent Event [Line Items]
Line of Credit Facility, Current Borrowing Capacity	$ 300.0
Base Rate [Member]
Subsequent Event [Line Items]
Basis Point Margin on Variable Rate Minimum	0
Basis Point Margin on Variable Rate Maximum	75
London Interbank Offered Rate (LIBOR) [Member]
Subsequent Event [Line Items]
Basis Point Margin on Variable Rate Minimum	100
Basis Point Margin on Variable Rate Maximum	175