Employee Benefits (Details) - Benefit Plans and Related Amounts Recorded in Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]
Projected benefit obligation	$ 45,450	$ 38,400	$ 35,870	$ 38,115
Pension plan assets at fair value	(18,475)	(14,465)	(13,190)
Funded status – shortfall	26,975	23,935	22,680
Amounts recorded in the Consolidated Balance Sheets for the plans:
Other liabilities — accrued pension obligation	26,975	23,935	22,680
Stockholders’ equity — deferred actuarial loss	$ (5,861)	$ (5,797)	$ (4,832)