Significant Accounting Policies - Newly Adopted Accounting Pronouncements (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Jan. 01, 2019
Newly-Adopted Accounting Pronouncements
Lease, Practical Expedients, Package [true false]	true
Right-of-use assets	$ 4,445
Lease liabilities	5,232
ASC 842
Newly-Adopted Accounting Pronouncements
Right-of-use assets	1,400	$ 3,800
Lease liabilities	$ 1,400	$ 4,700