Summary of Significant Accounting Policies - Insurance Coverage (Details) (USD $)	3 Months Ended
	Mar. 31, 2013 levels	Mar. 31, 2014	Dec. 31, 2013
Insurance Coverage [Line Items]
Levels of insurance coverage maintained by the Company	2
Amount in excess of primary insurance coverage			$ 100,000,000
Accrual for self-insurance liabilities		6,004,000	5,787,000
Other liability policies
Insurance Coverage [Line Items]
Primary limit of insurance coverage			1,000,000
Maritime employer's liability
Insurance Coverage [Line Items]
Primary limit of insurance coverage			10,000,000
Watercraft pollution policy
Insurance Coverage [Line Items]
Primary limit of insurance coverage			$ 5,000,000