Leases (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Leases [Abstract]
2014 (operating leases)	$ 16,113,000
2015 (operating leases)	10,614,000
2016 (operating leases)	8,321,000
2017 (operating leases)	7,420,000
2018 (operating leases)	6,877,000
After 2018 (operating leases)	52,231,000
Total minimum lease payments (operating leases)	101,576,000
2014 (capital leases)	76,000
2015 (capital leases)	76,000
2016 (capital leases)	76,000
2017 (capital leases)	76,000
2018 (capital leases)	76,000
After 2018 (capital leases)	0
Total minimum lease payments (capital leases)	380,000
Rental expense for operating leases	57,400,000	37,700,000	23,900,000
Sale Leaseback Transaction, Gross Proceeds			43,800,000
Sale Leaseback Transaction, Lease Terms			15
Minimum Lease Payments, Sale Leaseback Transactions			52,900,000
Sale Leaseback Transaction, Deferred Gain, Gross			$ 8,300,000