Debt (Details) (USD $)	6 Months Ended						1 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013	Oct. 22, 2013 Senior Unsecured Note	Jun. 30, 2014 Loan Agreement	Dec. 31, 2013 Loan Agreement	Jan. 31, 2014 Less unamortized deferred financing fees	Dec. 31, 2013 Less unamortized deferred financing fees	Jun. 30, 2014 Less unamortized deferred financing fees	May 30, 2014 Loan Agreement	May 29, 2014 Loan Agreement
Debt Instrument [Line Items]
Maximum borrowing capacity on line of credit										$ 300,000,000	$ 200,000,000
Remaining amount available under the line of credit					256,900,000
Letters of credit	4,600,000
Face amount on debt instruments				100,000,000
Long-term Debt	138,500,000		45,200,000		38,500,000	34,200,000
Unamortized debt issuance expense								853,000	766,000
Proceeds from long-term debt	$ 89,000,000	$ 0					$ 89,000,000	$ 11,000,000