Equity Investments (Schedule of Financial Information Related to Unconsolidated Entities Included in Consolidated Statement of Income) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Equity Investments [Abstract]
Revenues	$ 315,396	$ 317,317
Operating costs and expenses	283,365	277,256
Income from continuing operations before taxes	$ 32,008	$ 40,035