Financial Information for Guarantor Subsidiaries and Non-Guarantor Subsidiaries - Supplemental Condensed Consolidating Statement of Cash Flows (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Condensed Financial Statements
Net cash (used in) provided by operating activities	$ 279.5	$ 191.9
Cash flows from investing activities:
Capital expenditures	(140.2)	(132.6)
Acquisitions of businesses, net of cash acquired	(52.1)	0.0
Distributions of capital from equity investments	22.4	22.5
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	(159.9)	(104.0)
Cash flows from financing activities:
Net payments of long-term debt including proceeds and repurchases of senior notes and term loans	12.6	(80.1)
Payments of debt issuance and deferred financing costs	(27.7)	0.0
Payments on license obligations	(19.5)	(25.0)
Net redemptions of common stock under stock-based compensation plans and other	(3.9)	(4.4)
Other, principally change in intercompany financing activities	0.0	0.0
Net cash provided by (used in) financing activities	(38.5)	(109.5)
Effect of exchange rate changes on cash, cash equivalents and restricted cash	2.8	(1.9)
Increase (decrease) in cash, cash equivalents and restricted cash	83.9	(23.5)
Cash, cash equivalents and restricted cash, beginning of period	156.9	166.8
Cash, cash equivalents and restricted cash, end of period	240.8	143.3
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	(125.1)	(128.5)
Cash flows from investing activities:
Capital expenditures	(8.9)	(5.2)
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	(102.9)	210.7
Net cash used in investing activities	(111.8)	205.5
Cash flows from financing activities:
Net payments of long-term debt including proceeds and repurchases of senior notes and term loans	265.7	(76.5)
Payments of debt issuance and deferred financing costs	(27.7)
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	238.0	(76.5)
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	1.1	0.5
Cash, cash equivalents and restricted cash, beginning of period	1.7	0.0
Cash, cash equivalents and restricted cash, end of period	2.8	0.5
Reportable Legal Entities | SGC (Parent and Issuer)
Condensed Financial Statements
Net cash (used in) provided by operating activities	(101.1)	(119.9)
Cash flows from investing activities:
Capital expenditures	(25.1)	(26.7)
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	0.3
Other, principally intercompany balances	0.0	0.0
Net cash used in investing activities	(25.1)	(26.4)
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	(17.0)	(15.1)
Net redemptions of common stock under stock-based compensation plans and other	(3.9)	(4.4)
Other, principally change in intercompany financing activities	507.1	155.1
Net cash provided by (used in) financing activities	236.2	135.6
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	110.0	(10.7)
Cash, cash equivalents and restricted cash, beginning of period	32.7	43.2
Cash, cash equivalents and restricted cash, end of period	142.7	32.5
Reportable Legal Entities | Guarantor Subsidiaries
Condensed Financial Statements
Net cash (used in) provided by operating activities	327.9	331.9
Cash flows from investing activities:
Capital expenditures	(67.9)	(75.5)
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	7.9
Other, principally intercompany balances	0.0	0.0
Net cash used in investing activities	(86.7)	(67.6)
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	(2.5)	(9.9)
Net redemptions of common stock under stock-based compensation plans and other		0.0
Other, principally change in intercompany financing activities	(237.9)	(250.5)
Net cash provided by (used in) financing activities	(240.4)	(260.4)
Effect of exchange rate changes on cash, cash equivalents and restricted cash	0.0	(0.6)
Increase (decrease) in cash, cash equivalents and restricted cash	0.8	3.3
Cash, cash equivalents and restricted cash, beginning of period	41.0	37.7
Cash, cash equivalents and restricted cash, end of period	41.8	41.0
Reportable Legal Entities | Non-Guarantor Subsidiaries
Condensed Financial Statements
Net cash (used in) provided by operating activities	177.4	108.5
Cash flows from investing activities:
Capital expenditures	(38.3)	(25.2)
Acquisitions of businesses, net of cash acquired	(25.8)
Distributions of capital from equity investments	22.4	22.5
Changes in other assets and liabilities and other	2.5	(2.1)
Other, principally intercompany balances	(166.3)	0.0
Net cash used in investing activities	(205.5)	(4.8)
Cash flows from financing activities:
Net payments of long-term debt including proceeds and repurchases of senior notes and term loans	(3.1)	(3.6)
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	(115.3)
Net cash provided by (used in) financing activities	(3.1)	(118.9)
Effect of exchange rate changes on cash, cash equivalents and restricted cash	2.8	(1.3)
Increase (decrease) in cash, cash equivalents and restricted cash	(28.4)	(16.5)
Cash, cash equivalents and restricted cash, beginning of period	82.6	85.9
Cash, cash equivalents and restricted cash, end of period	54.2	69.4
Eliminating Entries
Condensed Financial Statements
Net cash (used in) provided by operating activities	0.4	(0.1)
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	269.2	(210.7)
Net cash used in investing activities	269.2	(210.7)
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	(269.2)	210.7
Net cash provided by (used in) financing activities	(269.2)	210.7
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	0.4	(0.1)
Cash, cash equivalents and restricted cash, beginning of period	(1.1)	0.0
Cash, cash equivalents and restricted cash, end of period	$ (0.7)	$ (0.1)