Significant Accounting Policies - Newly Adopted Accounting Pronouncements (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jan. 01, 2019
Newly-Adopted Accounting Pronouncements
Lease, Practical Expedients, Package [true false]	true
Right-of-use assets	$ 3,974
Lease liabilities	$ 4,405
ASC 842
Newly-Adopted Accounting Pronouncements
Right-of-use assets		$ 1,400	$ 3,800
Lease liabilities		$ 1,400	$ 4,700