Debt and Interest Expense Debt and Interest Expense (Narrative) (Details) $ in Millions	6 Months Ended
	Jun. 30, 2015 USD ($)	Mar. 27, 2015 USD ($) Rate
Debt Instrument [Line Items]
Debt Instrument, Offering Date	Mar. 27, 2015
Debt Instrument, Face Amount		$ 500.0
Debt Instrument, Interest Rate, Stated Percentage | Rate		5.25%
Debt Instrument, Maturity Date	Apr. 01, 2025
Sr. Notes Exchanged	$ 499.8
issuance cost on senior note	$ 6.5
Debt Instrument, Term Length	10 years
Line of Credit Facility [Abstract]
Debt Instrument, Unused Borrowing Capacity, Amount	$ 200.0
Minimum [Member]
Debt Instrument [Line Items]
Interest Coverage Ratio	3.0
Maximum [Member]
Debt Instrument [Line Items]
Leverage Ratio	2.5