Fair Value of Financial Instruments (Narrative) (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2014 Fair Value, Measurements, Recurring [Member] Fair Value, Inputs, Level 2 [Member]	Dec. 31, 2013 Fair Value, Measurements, Recurring [Member] Fair Value, Inputs, Level 2 [Member]	Mar. 31, 2014 Fair Value, Measurements, Recurring [Member] Fair Value, Inputs, Level 3 [Member]	Mar. 31, 2013 Fair Value, Measurements, Recurring [Member] Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of debt	$ 1,700,000,000	$ 1,700,000,000	$ 1,300,000,000	$ 1,300,000,000	$ 364,300,000	$ 390,100,000
Long-term Debt	$ 1,640,628,000	$ 1,663,226,000