Summary of Significant Accounting Policies - Debt Issuance Costs (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accounting Policies [Line Items]
Amortization of debt issuance costs	$ 627	$ 1,153	$ 1,135
Amortization of building financing costs	$ 31	$ 0	$ 0
Debt Issuance Cost [Member] | Minimum [Member]
Accounting Policies [Line Items]
Deferred Finance Costs, Amortization Period	5 years
Debt Issuance Cost [Member] | Maximum [Member]
Accounting Policies [Line Items]
Deferred Finance Costs, Amortization Period	7 years
Building Financing Cost [Member]
Accounting Policies [Line Items]
Deferred Building Financing Costs, Amortization Period	25 years