Acquisition (Details) (USD $)	0 Months Ended	12 Months Ended
	Dec. 17, 2012	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Business Acquisition [Line Items]
Indemnity holdback for any post-closing liabilities, amount		$ 0	$ 0	$ 4,000,000
Goodwill		22,900,000	22,900,000	22,800,000
Capital lease obligations		14,000,000	12,500,000
Acquisition related costs		1,400,000	2,500,000
Davenport [Member]
Business Acquisition [Line Items]
Total purchase consideration	41,200,000
Cash paid at closing for acquisition	34,300,000
Increase in total consideration			2,300,000
Indemnity holdback for any post-closing liabilities, amount	4,000,000
Period of time to release indemnity holdback	4 years
Contingent payments amount	600,000
Indemnity holdback liability obligations		2,000,000
Employment service provision obligations		0
Net deferred tax liabilities	1,000,000
Goodwill	6,700,000
Term of capital lease		10 years
Capital lease obligations		9,800,000
Acquisition related costs		0	1,600,000	1,300,000
Davenport [Member] | Non-competiiton agreements [Member]
Business Acquisition [Line Items]
Intangible assets	700,000
Intangible assets, useful life		5 years
Davenport [Member] | Customer relationships [Member]
Business Acquisition [Line Items]
Intangible assets	$ 1,900,000
Intangible assets, useful life		10 years