Other Income, Net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Other Income and Expenses [Abstract]
Interest income	$ 8,342	$ 5,737	$ 7,353
Other nonoperating income	2,981	3,514	4,866
Insurance policy expense (income), net	(3,373)	(3,851)	(6,923)
Other income, net	$ 7,950	$ 5,400	$ 5,296