Label	Element	Value
Stock Issued During Period, Value, Stock Options Exercised	us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised	$ 1,043,000
APIC, Share-based Payment Arrangement, Increase for Cost Recognition	us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	28,857,000
Stock Issued During Period, Value, Conversion of Units	us-gaap_StockIssuedDuringPeriodValueConversionOfUnits	0
Other Equity Activity, Value	sum_OtherEquityActivityValue	(1,458,000)
Noncontrolling Interest In Lp [Member]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	us-gaap_ProfitLoss	3,273,000
Stock Issued During Period, Value, Conversion of Units	us-gaap_StockIssuedDuringPeriodValueConversionOfUnits	(2,230,000)
Other Comprehensive Income (Loss), Net of Tax	us-gaap_OtherComprehensiveIncomeLossNetOfTax	58,000
AOCI Attributable to Parent [Member]
Other Comprehensive Income (Loss), Net of Tax	us-gaap_OtherComprehensiveIncomeLossNetOfTax	1,755,000
Additional Paid-in Capital [Member]
Stock Issued During Period, Value, Stock Options Exercised	us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised	1,042,000
APIC, Share-based Payment Arrangement, Increase for Cost Recognition	us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	28,857,000
Stock Issued During Period, Value, Conversion of Units	us-gaap_StockIssuedDuringPeriodValueConversionOfUnits	2,226,000
Other Equity Activity, Value	sum_OtherEquityActivityValue	(1,464,000)
Retained Earnings [Member]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	us-gaap_ProfitLoss	137,967,000
Common Class A [Member] | Common Stock [Member]
Stock Issued During Period, Value, Stock Options Exercised	us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised	$ 1,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period	us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised	54,517
Other Equity Activity, Shares	sum_OtherEquityActivityShares	650,206
Stock Issued During Period, Value, Conversion of Units	us-gaap_StockIssuedDuringPeriodValueConversionOfUnits	$ 4,000
Other Equity Activity, Value	sum_OtherEquityActivityValue	$ 6,000
Stock Issued During Period, Shares, Conversion of Units	us-gaap_StockIssuedDuringPeriodSharesConversionOfUnits	376,487