Income Taxes - Rollforward of Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reconciliation of unrecognized tax benefits
Balance at beginning of year	$ 663	$ 663	$ 3,700
Additions based on tax provisions related to the current year	0	0	0
Additions for tax positions of prior years	0	0	0
Reductions for tax positions of prior years	0	0	(3,037)
Settlements	0	0	0
Balance at end of year	$ 663	$ 663	$ 663