Accumulated Other Comprehensive Income Loss (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
AOCI Attributable to Parent, Net of Tax
Beginning balance			$ 934,389
Ending balance	$ 947,448		947,448
AOCI Attributable to Parent
AOCI Attributable to Parent, Net of Tax
Beginning balance	(3,746)	$ (3,273)	(3,838)	$ (4,205)
Other comprehensive income before reclassifications	113	215	205	1,147
Ending balance	$ (3,633)	$ (3,058)	$ (3,633)	$ (3,058)