Employee Benefits - Additional Information (Details) - USD ($)	1 Months Ended	12 Months Ended
	Apr. 30, 2013	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Postemployment Benefits [Abstract]
Funded percentage (greater than)			80.00%	80.00%
Contributions		$ 2,700,000	$ 2,500,000	$ 2,400,000
Companies contribution as percentage of total contributions made (less than)		5.00%	5.00%	5.00%
Multiple employer pension prepayment	$ 7,700,000				$ 7,700,000
Pension expense, inclusive of administrative fees		$ 3,600,000	$ 3,400,000	$ 3,300,000
Amortization of voluntary prepayment		$ 800,000	800,000	800,000
Matching contributions percentage		2.00%
Matching contributions		$ 240,000	$ 231,000	$ 224,000