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		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Equity Investments [Abstract]
Revenues	$ 320,281	$ 315,106	$ 635,677	$ 632,423
Operating costs and expenses	268,063	274,303	551,428	551,559
Income from continuing operations before taxes	$ 52,193	$ 40,781	$ 84,201	$ 80,816