Summary of Significant Accounting Policies - Deferred Financing (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Changes in deferred financing costs
Balance at the beginning of the period	$ 3,209	$ 4,033	$ 2,337
Deferred financing costs capitalized on new debt			2,320
Amortization of deferred financing costs	(823)	(824)	(624)
Balance at the end of the period	$ 2,386	$ 3,209	$ 4,033