Employee and Contract Termination Costs - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Restructuring Cost And Reserve [Line Items]
Reduction of net income related to voluntary early retirement and termination costs									$ 11,100	$ 8,900
Net income attributable to SNI	$ 164,708	$ 124,559	$ 193,718	$ 123,843	$ 131,846	$ 131,339	$ 153,794	$ 128,296	606,828	545,275	$ 505,070
Contract termination costs									9,700
Voluntary Early Retirement Program and Employee Termination [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring charges									17,900	$ 14,400
Reorganization [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring charges									$ 3,866
Costs for severance, retention and related benefit cost	3,900
Net income attributable to SNI	$ (2,400)