Summary of Significant Accounting Policies - Debt Issuance Costs (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accounting Policies [Line Items]
Amortization of debt issuance costs	$ 644,000	$ 778,000	$ 627,000
Amortization of building financing costs	0	$ 124,000	$ 31,000
Write-off of unamortized debt issuance cost	$ 3,005,000
Debt Issuance Cost [Member] | Minimum [Member]
Accounting Policies [Line Items]
Debt issuance costs, amortization period (in years)	5 years
Debt Issuance Cost [Member] | Maximum [Member]
Accounting Policies [Line Items]
Debt issuance costs, amortization period (in years)	7 years
Building Financing Cost [Member]
Accounting Policies [Line Items]
Deferred building financing costs, amortization period (in years)	25 years