Supplemental Cash Flow Information (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Supplemental Cash Flow Information
Income taxes paid, net of refunds	$ 65,511	$ 57,663	$ 50,324
Interest paid	2,264	1,594	1,521
Assets acquired through capital leases	$ 29,739