Leases (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Leases (Details)
2012 (operating leases)	$ 6,605,000
2013 (operating leases)	3,128,000
2014 (operating leases)	1,660,000
2015 (operating leases)	838,000
2016 (operating leases)	501,000
After 2016 (operating leases)	981,000
Total minimum lease payments (operating leases)	13,713,000
2012 (capital leases)	76,000
2013 (capital leases)	76,000
2014 (capital leases)	76,000
2015 (capital leases)	76,000
2016 (capital leases)	76,000
After 2016 (capital leases)	228,000
Total minimum lease payments (capital leases)	608,000
Rental expense for operating leases	$ 18,500,000	$ 10,900,000	$ 10,000,000