Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net earnings	$ 971,772	$ 658,645	$ 696,067
Other comprehensive income, net of tax:
Foreign currency translation adjustments	138,525	(111,960)	(139,789)
Unrecognized pension gain	0	0	(1,063)
Total other comprehensive income/(loss), net of tax	138,525	(111,960)	(140,852)
Comprehensive income	$ 1,110,297	$ 546,685	$ 555,215