Long-Term Debt (Details) (Revolving credit facility, USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revolving credit facility
Line of Credit Facility [Line Items]
Interest incurred	$ 2,295	$ 2,090	$ 2,936
Capitalized interest	563	935	1,026
Interest paid (net of capitalized interest)	$ 1,314	$ 618	$ 1,498
Weighted average interest rate	2.20%	3.70%	2.30%