Summary of Significant Accounting Policies (Tax Effects of Componenets of Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Summary of Significant Accounting Policies [Abstract]
Defined benefit pension plan adjustments, Before-Tax Amount	$ 31	$ (13,887)	$ 18,675
Defined benefit pension plan adjustments, Tax (Expense) Benefit	1,995	5,732	(7,765)
Defined benefit pension plan adjustments, Net-of-Tax Amount	2,026	(8,155)	10,910
Foreign currency translation adjustment, Before-Tax Amount	(5,897)	(1,086)	(1,212)
Foreign currency translation adjustment, Tax (Expense) Benefit	2,683	448	474
Foreign currency translation adjustment, Net-of-Tax Amount	(3,214)	(638)	(738)
Unrealized gain (loss) in fair value of investments, Before-Tax Amount	1,123	346	(744)
Unrealized gain (loss) in fair value of investments, Tax (Expense) Benefit	(357)	(141)	189
Unrealized gain (loss) in fair value of investments, Net-of-Tax Amount	766	205	(555)
Unrealized gain (loss) in fair value of interest rate swap, Before-Tax Amount	(37)	594	948
Unrealized gain (loss) in fair value of interest rate swap, Tax (Expense) Benefit	(88)	(245)	(370)
Unrealized gain (loss) in fair value of interest rate swap, Net-of-Tax Amount	(125)	349	578
Total other comprehensive (loss) income, Before-Tax Amount	(4,780)	(14,033)	17,667
Total other comprehensive (loss) income, Tax (Expense) Benefit	4,233	5,794	(7,472)
Total other comprehensive (loss) income, net of tax	$ (547)	$ (8,239)	$ 10,195