Commitments and Contingencies (Details Textual) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Minimum Period Of Lease Including Renewal Options Operating Leases	5 years
Maximum Period Of Lease Including Renewal Options Operating Leases	35 years
Commitments and Contingencies (Textual) [Abstract]
Additional payment if specified financial criteria are attained based on contractual arrangement	$ 1,600,000
Total rent expense	66,000,000	55,200,000	51,900,000
Total rental income	955,000	920,000	726,000
Purchase commitments of products and services through 2016	31,000,000
Total outstanding holdbacks	2,200,000	1,500,000
Amount paid to sellers for unused portion of holdbacks	$ 2,700,000	$ 1,800,000	$ 3,300,000