Financial Information for Guarantor Subsidiaries and Non-Guarantor Subsidiaries - Supplemental Condensed Consolidating Statement of Cash Flows (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Condensed Financial Statements
Net cash (used in) provided by operating activities	$ 389.0	$ 342.8
Cash flows from investing activities:
Capital expenditures	(214.1)	(214.4)
Acquisitions of businesses, net of cash acquired	(57.7)	0.0
Distributions of capital from equity investments	23.9	24.0
Changes in other assets and liabilities and other	10.0	6.1
Other, principally intercompany balances	0.0	0.0
Net cash used in investing activities	(237.9)	(184.3)
Cash flows from financing activities:
Net payments of long-term debt including proceeds and repurchases of senior notes and term loans	10.9	(122.5)
Payments of debt issuance and deferred financing costs	(52.3)	0.0
Payments on license obligations	(29.0)	(34.5)
Net redemptions of common stock under stock-based compensation plans and other	(2.7)	(4.7)
Other, principally change in intercompany financing activities	0.0	0.0
Net cash provided by (used in) financing activities	(73.1)	(161.7)
Effect of exchange rate changes on cash, cash equivalents and restricted cash	4.8	(1.1)
Increase (decrease) in cash, cash equivalents and restricted cash	82.8	(4.3)
Cash, cash equivalents and restricted cash, beginning of period	156.9	166.8
Cash, cash equivalents and restricted cash, end of period	239.7	162.5
SGI (Issuer)
Cash flows from financing activities:
Net redemptions of common stock under stock-based compensation plans and other	0.0
Guarantor Subsidiaries
Cash flows from financing activities:
Net redemptions of common stock under stock-based compensation plans and other	0.0
Reportable Legal Entities | SGI (Issuer)
Condensed Financial Statements
Net cash (used in) provided by operating activities	(169.9)	(157.0)
Cash flows from investing activities:
Capital expenditures	(13.6)	(22.1)
Acquisitions of businesses, net of cash acquired	0.0
Distributions of capital from equity investments	0.0	0.0
Changes in other assets and liabilities and other	0.0	0.0
Other, principally intercompany balances	(27.7)	296.8
Net cash used in investing activities	(41.3)	274.7
Cash flows from financing activities:
Net payments of long-term debt including proceeds and repurchases of senior notes and term loans	265.7	(117.2)
Payments of debt issuance and deferred financing costs	(52.3)
Payments on license obligations	0.0	0.0
Net redemptions of common stock under stock-based compensation plans and other		0.0
Other, principally change in intercompany financing activities	0.0	0.0
Net cash provided by (used in) financing activities	213.4	(117.2)
Effect of exchange rate changes on cash, cash equivalents and restricted cash	0.0	0.0
Increase (decrease) in cash, cash equivalents and restricted cash	2.2	0.5
Cash, cash equivalents and restricted cash, beginning of period	1.7	0.0
Cash, cash equivalents and restricted cash, end of period	3.9	0.5
Reportable Legal Entities | SGC (Parent and Issuer)
Condensed Financial Statements
Net cash (used in) provided by operating activities	(162.6)	(213.3)
Cash flows from investing activities:
Capital expenditures	(42.0)	(36.6)
Acquisitions of businesses, net of cash acquired	0.0
Distributions of capital from equity investments	0.0	0.0
Changes in other assets and liabilities and other	0.0	0.0
Other, principally intercompany balances	0.0	0.0
Net cash used in investing activities	(42.0)	(36.6)
Cash flows from financing activities:
Net payments of long-term debt including proceeds and repurchases of senior notes and term loans	(250.0)	0.0
Payments of debt issuance and deferred financing costs	0.0
Payments on license obligations	(24.3)	(24.2)
Net redemptions of common stock under stock-based compensation plans and other	(2.7)	(4.7)
Other, principally change in intercompany financing activities	586.2	278.3
Net cash provided by (used in) financing activities	309.2	249.4
Effect of exchange rate changes on cash, cash equivalents and restricted cash	0.0	0.0
Increase (decrease) in cash, cash equivalents and restricted cash	104.6	(0.5)
Cash, cash equivalents and restricted cash, beginning of period	32.7	43.2
Cash, cash equivalents and restricted cash, end of period	137.3	42.7
Reportable Legal Entities | Guarantor Subsidiaries
Condensed Financial Statements
Net cash (used in) provided by operating activities	471.5	494.3
Cash flows from investing activities:
Capital expenditures	(96.4)	(110.4)
Acquisitions of businesses, net of cash acquired	(26.3)
Distributions of capital from equity investments	0.0	0.0
Changes in other assets and liabilities and other	7.5	6.1
Other, principally intercompany balances	0.0	0.0
Net cash used in investing activities	(115.2)	(104.3)
Cash flows from financing activities:
Net payments of long-term debt including proceeds and repurchases of senior notes and term loans	0.0	0.0
Payments of debt issuance and deferred financing costs	0.0
Payments on license obligations	(4.7)	(10.3)
Net redemptions of common stock under stock-based compensation plans and other		0.0
Other, principally change in intercompany financing activities	(350.1)	(376.3)
Net cash provided by (used in) financing activities	(354.8)	(386.6)
Effect of exchange rate changes on cash, cash equivalents and restricted cash	0.0	(0.4)
Increase (decrease) in cash, cash equivalents and restricted cash	1.5	3.0
Cash, cash equivalents and restricted cash, beginning of period	41.0	37.7
Cash, cash equivalents and restricted cash, end of period	42.5	40.7
Reportable Legal Entities | Non-Guarantor Subsidiaries
Condensed Financial Statements
Net cash (used in) provided by operating activities	254.3	225.9
Cash flows from investing activities:
Capital expenditures	(62.1)	(45.3)
Acquisitions of businesses, net of cash acquired	(31.4)
Distributions of capital from equity investments	23.9	24.0
Changes in other assets and liabilities and other	2.5	0.0
Other, principally intercompany balances	(208.4)	(198.8)
Net cash used in investing activities	(275.5)	(220.1)
Cash flows from financing activities:
Net payments of long-term debt including proceeds and repurchases of senior notes and term loans	(4.8)	(5.3)
Payments of debt issuance and deferred financing costs	0.0
Payments on license obligations	0.0	0.0
Net redemptions of common stock under stock-based compensation plans and other	0.0	0.0
Other, principally change in intercompany financing activities	0.0	0.0
Net cash provided by (used in) financing activities	(4.8)	(5.3)
Effect of exchange rate changes on cash, cash equivalents and restricted cash	4.8	(0.7)
Increase (decrease) in cash, cash equivalents and restricted cash	(21.2)	(0.2)
Cash, cash equivalents and restricted cash, beginning of period	82.6	85.9
Cash, cash equivalents and restricted cash, end of period	61.4	85.7
Eliminating Entries
Condensed Financial Statements
Net cash (used in) provided by operating activities	(4.3)	(7.1)
Cash flows from investing activities:
Capital expenditures	0.0	0.0
Acquisitions of businesses, net of cash acquired	0.0
Distributions of capital from equity investments	0.0	0.0
Changes in other assets and liabilities and other	0.0	0.0
Other, principally intercompany balances	236.1	(98.0)
Net cash used in investing activities	236.1	(98.0)
Cash flows from financing activities:
Net payments of long-term debt including proceeds and repurchases of senior notes and term loans	0.0	0.0
Payments of debt issuance and deferred financing costs	0.0
Payments on license obligations	0.0	0.0
Net redemptions of common stock under stock-based compensation plans and other	0.0	0.0
Other, principally change in intercompany financing activities	(236.1)	98.0
Net cash provided by (used in) financing activities	(236.1)	98.0
Effect of exchange rate changes on cash, cash equivalents and restricted cash	0.0	0.0
Increase (decrease) in cash, cash equivalents and restricted cash	(4.3)	(7.1)
Cash, cash equivalents and restricted cash, beginning of period	(1.1)	0.0
Cash, cash equivalents and restricted cash, end of period	$ (5.4)	$ (7.1)