Label	Element	Value
Reclassification from Noncontrolling Interest to Redeemable Noncontrolling Interest	stgw_ReclassificationFromNoncontrollingInterestToRedeemableNoncontrollingInterest	$ (27,955,000)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	us-gaap_ProfitLoss	8,896,000
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	us-gaap_ProfitLoss	27,435,000
APIC, Share-Based Payment Arrangement, Increase for Cost Recognition	us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	70,427,000
Stock Issued During Period, Value, Noncontrolling Interest, Increase from Business Combination	stgw_StockIssuedDuringPeriodValueNoncontrollingInterestIncreaseFromBusinessCombination	778,658,000
Stockholders' Equity, Other	us-gaap_StockholdersEquityOther	(2,026,000)
Stockholders Equity, Tax Impact on Step Up Transactions	stgw_StockholdersEquityTaxImpactOnStepUpTransactions	23,108,000
Stockholders Equity, Impact of Adjustment on Noncontrolling Interest	stgw_StockholdersEquityImpactOfAdjustmentOnNoncontrollingInterest	7,297,000
Stockholders' Equity, Other1	stgw_StockholdersEquityOther1	300,000
Stock Repurchased and Retired During Period, Value	us-gaap_StockRepurchasedAndRetiredDuringPeriodValue	841,000
Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests	us-gaap_MinorityInterestDecreaseFromRedemptions	157,267,000
Contribution from Limited Liability Company (LLC)	stgw_ContributionFromLimitedLiabilityCompanyLLC	250,000
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders	us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders	16,338,000
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders	us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders	11,936,000
Member Units [Member]
Other Comprehensive Income (Loss), Net of Tax	us-gaap_OtherComprehensiveIncomeLossNetOfTax	(375,000)
Redeemable noncontrolling interest, changes in redemption value	stgw_Redeemablenoncontrollinginterestchangesinredemptionvalue	72,000
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	us-gaap_ProfitLoss	24,742,000
Stock Issued During Period, Value, Noncontrolling Interest, Increase from Business Combination	stgw_StockIssuedDuringPeriodValueNoncontrollingInterestIncreaseFromBusinessCombination	(178,372,000)
Distribution Made to Limited Liability Company (LLC) Member, Cash Distributions Declared	us-gaap_DistributionMadeToLimitedLiabilityCompanyLLCMemberCashDistributionsDeclared	204,929,000
Contribution from Limited Liability Company (LLC)	stgw_ContributionFromLimitedLiabilityCompanyLLC	250,000
Retained Earnings [Member]
Redeemable noncontrolling interest, changes in redemption value	stgw_Redeemablenoncontrollinginterestchangesinredemptionvalue	3,834,000
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	us-gaap_ProfitLoss	(3,706,000)
Stockholders' Equity, Other	us-gaap_StockholdersEquityOther	(558,000)
Additional Paid-in Capital [Member]
Reclassification from Noncontrolling Interest to Redeemable Noncontrolling Interest	stgw_ReclassificationFromNoncontrollingInterestToRedeemableNoncontrollingInterest	(25,236,000)
APIC, Share-Based Payment Arrangement, Increase for Cost Recognition	us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	70,427,000
Stock Issued During Period, Value, Noncontrolling Interest, Increase from Business Combination	stgw_StockIssuedDuringPeriodValueNoncontrollingInterestIncreaseFromBusinessCombination	110,555,000
Stockholders' Equity, Other	us-gaap_StockholdersEquityOther	(228,000)
Stock Issued During Period, Value, Restricted Stock Award, Gross	us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardGross	(2,000)
Stock Issued During Period, Value, Conversion of Units	us-gaap_StockIssuedDuringPeriodValueConversionOfUnits	209,947,000
Stockholders Equity, Tax Impact on Step Up Transactions	stgw_StockholdersEquityTaxImpactOnStepUpTransactions	23,108,000
Stockholders Equity, Impact of Adjustment on Noncontrolling Interest	stgw_StockholdersEquityImpactOfAdjustmentOnNoncontrollingInterest	8,845,000
Stock Repurchased and Retired During Period, Value	us-gaap_StockRepurchasedAndRetiredDuringPeriodValue	841,000
Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests	us-gaap_MinorityInterestDecreaseFromRedemptions	14,138,000
Noncontrolling Interest [Member]
Reclassification from Noncontrolling Interest to Redeemable Noncontrolling Interest	stgw_ReclassificationFromNoncontrollingInterestToRedeemableNoncontrollingInterest	(2,719,000)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	us-gaap_ProfitLoss	2,693,000
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	us-gaap_ProfitLoss	12,602,000
Stock Issued During Period, Value, Noncontrolling Interest, Increase from Business Combination	stgw_StockIssuedDuringPeriodValueNoncontrollingInterestIncreaseFromBusinessCombination	636,416,000
Stockholders' Equity, Other	us-gaap_StockholdersEquityOther	(1,240,000)
Stockholders Equity, Impact of Adjustment on Noncontrolling Interest	stgw_StockholdersEquityImpactOfAdjustmentOnNoncontrollingInterest	(1,549,000)
Stockholders' Equity, Other1	stgw_StockholdersEquityOther1	300,000
Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests	us-gaap_MinorityInterestDecreaseFromRedemptions	143,134,000
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders	us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders	16,338,000
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders	us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders	11,936,000
Preferred Stock [Member]
Stock Issued During Period, Value, Noncontrolling Interest, Increase from Business Combination	stgw_StockIssuedDuringPeriodValueNoncontrollingInterestIncreaseFromBusinessCombination	$ 209,980,000
Stock Issued During Period, Shares, Conversion of Units	us-gaap_StockIssuedDuringPeriodSharesConversionOfUnits	(123,849,000)
Stock Issued During Period, Value, Conversion of Units	us-gaap_StockIssuedDuringPeriodValueConversionOfUnits	$ (209,980,000)
Stock Issued During Period, Noncontrolling Interest, Increase from Business Combination	stgw_StockIssuedDuringPeriodNoncontrollingInterestIncreaseFromBusinessCombination	123,849,000
Parent [Member]
Reclassification from Noncontrolling Interest to Redeemable Noncontrolling Interest	stgw_ReclassificationFromNoncontrollingInterestToRedeemableNoncontrollingInterest	$ (25,236,000)
Other Comprehensive Income (Loss), Net of Tax	us-gaap_OtherComprehensiveIncomeLossNetOfTax	(375,000)
Other Comprehensive Income (Loss), Net of Tax	us-gaap_OtherComprehensiveIncomeLossNetOfTax	(5,278,000)
Redeemable noncontrolling interest, changes in redemption value	stgw_Redeemablenoncontrollinginterestchangesinredemptionvalue	3,834,000
Redeemable noncontrolling interest, changes in redemption value	stgw_Redeemablenoncontrollinginterestchangesinredemptionvalue	72,000
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	us-gaap_ProfitLoss	(3,706,000)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	us-gaap_ProfitLoss	24,742,000
APIC, Share-Based Payment Arrangement, Increase for Cost Recognition	us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	70,427,000
Stock Issued During Period, Value, Noncontrolling Interest, Increase from Business Combination	stgw_StockIssuedDuringPeriodValueNoncontrollingInterestIncreaseFromBusinessCombination	142,242,000
Stockholders' Equity, Other	us-gaap_StockholdersEquityOther	(786,000)
Stockholders Equity, Tax Impact on Step Up Transactions	stgw_StockholdersEquityTaxImpactOnStepUpTransactions	23,108,000
Stockholders Equity, Impact of Adjustment on Noncontrolling Interest	stgw_StockholdersEquityImpactOfAdjustmentOnNoncontrollingInterest	8,846,000
Stock Repurchased and Retired During Period, Value	us-gaap_StockRepurchasedAndRetiredDuringPeriodValue	841,000
Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests	us-gaap_MinorityInterestDecreaseFromRedemptions	14,133,000
Distribution Made to Limited Liability Company (LLC) Member, Cash Distributions Declared	us-gaap_DistributionMadeToLimitedLiabilityCompanyLLCMemberCashDistributionsDeclared	204,929,000
Contribution from Limited Liability Company (LLC)	stgw_ContributionFromLimitedLiabilityCompanyLLC	250,000
Common Class C [Member] | Common Stock [Member]
Stock Issued During Period, Value, Noncontrolling Interest, Increase from Business Combination	stgw_StockIssuedDuringPeriodValueNoncontrollingInterestIncreaseFromBusinessCombination	$ 2,000
Stock Issued During Period, Noncontrolling Interest, Increase from Business Combination	stgw_StockIssuedDuringPeriodNoncontrollingInterestIncreaseFromBusinessCombination	179,970,000
Common Class A and B [Member] | Common Stock [Member]
Stock Issued During Period, Shares, Restricted Stock Award, Gross	us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardGross	1,962,000
Stock Issued During Period, Value, Noncontrolling Interest, Increase from Business Combination	stgw_StockIssuedDuringPeriodValueNoncontrollingInterestIncreaseFromBusinessCombination	$ 77,000
Stock Issued During Period, Shares, Conversion of Units	us-gaap_StockIssuedDuringPeriodSharesConversionOfUnits	33,035,000
Stock Issued During Period, Value, Restricted Stock Award, Gross	us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardGross	$ 2,000
Stock Issued During Period, Value, Conversion of Units	us-gaap_StockIssuedDuringPeriodValueConversionOfUnits	33,000
Stockholders Equity, Impact of Adjustment on Noncontrolling Interest	stgw_StockholdersEquityImpactOfAdjustmentOnNoncontrollingInterest	1,000
Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests	us-gaap_MinorityInterestDecreaseFromRedemptions	$ (5,000)
Stock Repurchased and Retired During Period, Shares	us-gaap_StockRepurchasedAndRetiredDuringPeriodShares	14,000
Stock Issued During Period, Noncontrolling Interest, Increase from Business Combination	stgw_StockIssuedDuringPeriodNoncontrollingInterestIncreaseFromBusinessCombination	78,794,000
Stock Issued During Period, Shares, Conversion of Convertible Securities	us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities	4,476,000