Fair Value Measurements Narrative (Details) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2014 Fair Value, Inputs, Level 2 [Member] $250 Million Senior Notes [Member]	Dec. 31, 2013 Fair Value, Inputs, Level 2 [Member] $250 Million Senior Notes [Member]	Mar. 31, 2014 Fair Value, Inputs, Level 2 [Member] $400 Million Senior Notes [Member]	Dec. 31, 2013 Fair Value, Inputs, Level 2 [Member] $400 Million Senior Notes [Member]
Fair Value Measurements [Line Items]
Defined benefit plan, transfers between measurement levels	$ 0
Debt instrument fair value		$ 270,000,000	$ 261,250,000	$ 424,000,000	$ 416,000,000