Fair Value of Financial Instruments (Assets and Liabilites Measured on a Non-Recurring Basis) (Narrative) (Details) - Senior Notes [Member] - 4.875% Senior Notes [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Financial Instruments Measured on a Non-Recurring Basis [Line Items]
Debt instrument, interest rate (percentage)	4.875%
Fair Value Measurements, Non-Recurring [Member] | Level 1 [Member]
Fair Value, Financial Instruments Measured on a Non-Recurring Basis [Line Items]
Fair value measurements, valuation techniques	the estimated fair value of the 4.875% Senior Notes, based on quoted market prices in active markets, a Level 1 input
Fair Value Measurements, Non-Recurring [Member] | Carrying Amount [Member]
Fair Value, Financial Instruments Measured on a Non-Recurring Basis [Line Items]
4.875% Senior Notes (in dollars)	$ 400.0	$ 400.0
Fair Value Measurements, Non-Recurring [Member] | Fair Value [Member] | Level 1 [Member]
Fair Value, Financial Instruments Measured on a Non-Recurring Basis [Line Items]
4.875% Senior Notes (in dollars)	$ 344.0	$ 375.0