Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of year	$ 2,499	$ 0	$ 0
Increases (decreases) for tax positions of current year	0	2,499	0
Decreases for dispositions and other	(1,449)	0	0
Balance at end of year	$ 1,050	$ 2,499	$ 0