Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statement of Comprehensive Income [Abstract]
Net income	$ 431,620	$ 450,003	$ 461,443
Foreign currency translation	(61,728)	11,843	17,279
Unrealized (losses) gains on investments before reclassifications	(532)	134	(27)
Amounts reclassified to other expense for unrealized (losses) gains on investments		1,575
Amounts reclassified to selling and administrative expenses for unrealized (losses) gains on investments			(968)
Unrealized (losses) gains on investments before income taxes	(532)	1,709	(995)
Income tax benefit (expense) on unrealized (losses) gains on investments	43	(639)	348
Unrealized (losses) gains on investments, net of tax	(489)	1,070	(647)
Retirement liability adjustment before reclassifications	(34,797)	27,888	(14,147)
Retirement liability amounts reclassified to selling and administrative expenses	2,886	3,678	3,055
Retirement liability adjustment	(31,911)	31,566	(11,092)
Income tax benefit (expense) on retirement liability adjustment	9,544	(12,205)	4,120
Retirement liability adjustment, net of tax	(22,367)	19,361	(6,972)
Other comprehensive (loss) income	(84,584)	32,274	9,660
Comprehensive income	$ 347,036	$ 482,277	$ 471,103