Stock Based Compensation Plans (Employee Stock Purchase Plan and Other Incentive Plans Narrative) (Details) - USD ($)	3 Months Ended		12 Months Ended
	Jan. 31, 2020	Oct. 31, 2019	Oct. 31, 2019	Oct. 31, 2018	Oct. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Based Compensation Expense Net Total			$ 91,913,000	$ 88,055,000	$ 80,049,000
Fixed exchange ratio, closing price observed on same date		$ 44.34	$ 44.34
Restricted Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost related to awards issued under the plan, not yet recognized		$ 134,900,000	$ 134,900,000
Weighted-average period over which compensation cost related to awards issued under subsidiary plan is expected to be recognized (in years)			2 years 8 months 12 days
Granted, weighted-average grant date fair value ($ per share)			$ 44.87
Granted shares			1,746,000
Phantom Incentive Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			5 years
Phantom Incentive Units [Member] | Scenario, Forecast [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, weighted-average grant date fair value ($ per share)	$ 150.42
Granted shares	23,938,000
Employee stock purchase plans [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-Voting stock reserved for issuance under the 2013 Qualified Employee Stock Purchase Plan			500,000
Stock Issued Reserved For Issuance Shares Employee Stock Purchase Plans, Non-Qualified			100,000
Cumulative Non-Voting Common Stock issued under the Qualified and Nonqualified Employee Stock Purchase Plans			500,000
Proceeds from issuance of Non-voting Common stock			$ 3,200,000	3,200,000	3,000,000.0
Maximum amount purchase of Non-Voting Common Stock permitted per six months			$ 12,500
Percent of market price for Non-Voting Common Stock purchases by eligible employees			90.00%
Stock Based Compensation Expense Net Total			$ 355,000	793,000	716,000
Employee Stock Purchase Incentive Plans [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-Voting Common stock reserved for issuance under the Employee Stock Purchase incentive Plan			900,000
Non-voting Common stock issued under the Employee Stock Purchase Incentive Plan			600,000
Proceeds from issuance of Non-voting Common stock			$ 4,600,000	4,900,000	4,000,000.0
Percent of market price for Non-Voting Common Stock purchases by eligible employees			90.00%
Stock Based Compensation Expense Net Total			$ 512,000	877,000	753,000
Atlanta Capital Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Based Compensation Expense Net Total			$ 2,280,000	$ 2,969,000	3,420,000
Atlanta Capital Long Term Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Profit interest units issued during the year			0	0
Compensation cost related to awards issued under the plan, not yet recognized		2,400,000	$ 2,400,000
Weighted-average period over which compensation cost related to awards issued under subsidiary plan is expected to be recognized (in years)			1 year 8 months 12 days
Cumulative profit units granted			323,016
Vesting period			5 years
Atlanta Capital Phantom Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost related to awards issued under the plan, not yet recognized		3,800,000	$ 3,800,000
Weighted-average period over which compensation cost related to awards issued under subsidiary plan is expected to be recognized (in years)			3 years 6 months
Atlanta Capital Phantom Incentive Plan [Member] | Phantom Incentive Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, weighted-average grant date fair value ($ per share)			$ 133.12
Granted shares			19,531,000
Parametric Long Term Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Based Compensation Expense Net Total		1,600,000	$ 3,461,000	$ 3,177,000	$ 3,816,000
Parametric Phantom Incentive Plan 2016 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost related to awards issued under the plan, not yet recognized		$ 100,000	$ 100,000
Weighted-average period over which compensation cost related to awards issued under subsidiary plan is expected to be recognized (in years)			2 years 8 months 12 days
Fixed exchange ratio, per unit price		$ 2,939	$ 2,939
Parametric Phantom Incentive Plan 2018 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost related to awards issued under the plan, not yet recognized		$ 100,000	$ 100,000
Weighted-average period over which compensation cost related to awards issued under subsidiary plan is expected to be recognized (in years)			4 years
Fixed exchange ratio, per unit price		$ 29.39	$ 29.39
Stock Option Income Deferral Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total shares exercised and placed in trust with the Company			200,000