Other Income, Net (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Other Income and Expenses [Abstract]
Interest income	$ 843	$ 772	$ 1,757	$ 1,800
Other nonoperating income	637	798	1,519	1,366
Insurance policy expense	(158)	(20)	(377)	(584)
Other income, net	$ 1,322	$ 1,550	$ 2,899	$ 2,582