Operations by Business Segment and Geographic Information Geographic Information (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Segment Reporting Information [Line Items]
Revenues	$ 713,848	$ 680,153	$ 646,034
Long-Lived Assets	181,362	169,183	157,229
United States [Member]
Segment Reporting Information [Line Items]
Revenues	637,524	607,339	577,613
Long-Lived Assets	166,598	153,946	141,108
Canada [Member]
Segment Reporting Information [Line Items]
Revenues	76,324	72,814	68,421
Long-Lived Assets	$ 14,764	$ 15,237	$ 16,121