CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 814,351	$ 847,448	$ 778,473
Other comprehensive income (loss), net of tax:
Foreign currency translation, net of tax: 2017 - ($109); 2016 - ($3,652); 2015 - $1,695	353,523	(226,355)	(76,937)
Pension plan and SERP liability, net of tax: 2017 - $2,069; 2016 - $4,067; 2015 - ($1,878)	(3,576)	(6,999)	775
Comprehensive income	1,164,298	614,094	702,311
Less: comprehensive income attributable to non-controlling interests	(190,471)	(173,967)	(167,825)
Comprehensive income attributable to SNI	$ 973,827	$ 440,127	$ 534,486