Significant Accounting Policies - Cash, Cash Equivalents and Restricted Cash (Details) - USD ($)	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015
Accounting Policies [Abstract]
Cash and cash equivalents	$ 95,063,000	$ 73,475,000	$ 83,336,000	$ 69,959,000
Restricted cash	17,660,000	20,950,000
Cash, Cash Equivalents And Restricted Cash	$ 112,723,000	$ 94,425,000	$ 83,336,000	$ 69,959,000