Annual report pursuant to Section 13 and 15(d)

Income taxes Income taxes - Reconciliation of Tax Provision Using the Federal Statutory Income Tax Rate to Reported Provision (Details)

v3.8.0.1
Income taxes Income taxes - Reconciliation of Tax Provision Using the Federal Statutory Income Tax Rate to Reported Provision (Details) - USD ($)
$ in Thousands
12 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2015
Reconciliation of actual provision for income taxes and provision for income taxes resulting from the use of federal statutory income tax      
Federal income tax provision at statutory rate of 35% $ 109,982 $ 100,089 $ 90,937
State income taxes, net of federal benefit 10,554 10,723 9,847
Foreign taxation (6,940) (3,976) (2,208)
Permanent items 970 1,284 1,602
Tax credits (4,851) (1,592) (961)
Vesting of equity compensation (6,569) 0 0
Other (1,093) (720) 553
Provision for income taxes $ 102,053 $ 105,808 $ 99,770
Statutory income tax rate (as a percent) 35.00% 35.00% 35.00%