Business Segments and Geographic Areas (Details 3) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Operating revenues:
Total operating revenues	$ 646,686	$ 539,626	$ 516,935
Long-Lived Assets:
Property and equipment - net	749,501	659,756
United States [Member]
Operating revenues:
Total operating revenues	618,270	527,945	509,221
Long-Lived Assets:
Property and equipment - net	723,977	652,948
International [Member]
Operating revenues:
Total operating revenues	28,416	11,681	7,714
Long-Lived Assets:
Property and equipment - net	$ 25,524	$ 6,808