Other Income, Net (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Other Income and Expenses [Abstract]
Interest income	$ 3,800	$ 4,070
Other nonoperating income	3,645	680
Insurance policy expense	(999)	(500)
Other income, net	$ 6,446	$ 4,250