Share-Based Compensation (Stock Option Activity) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2019
Share-based Payment Arrangement [Abstract]
Intrinsic value, exercises in period	$ 6,011
Options
Outstanding at beginning of the period (shares)	8,619,000
Granted (shares)	5,000
Exercised (shares)	(430,000)
Cancelled (shares)	(1,000)
Forfeited (shares)	(32,000)
Expired (shares)	0
Outstanding at end of the period (shares)	8,161,000
Options exercisable (shares)	5,835,000
Options vested and expected to vest (shares)	8,142,000
Weighted Average Exercise Price/Share
Weighted average exercise price, outstanding, beginning balance (in dollars per share)	$ 8.15
Weighted average exercise price, granted (in dollars per share)	18.82
Weighted average exercise price, exercised (in dollars per share)	5.22
Weighted average exercise price, cancelled (in dollars per share)	20.88
Weighted average exercise price, forfeited (in dollars per share)	16.52
Weighted average exercise price, expired (in dollars per share)	0
Weighted average exercise price, outstanding, ending balance (in dollars per share)	8.28
Weighted average exercise price, exercisable (in dollars per share)	5.74
Weighted average exercise price, options vested and expected to vest (in dollars per share)	$ 8.27
Weighted Average Remaining Contractual Term
Weighted average remaining contractual term, outstanding	6 years	6 years 3 months
Weighted average contractual term, exercisable	5 years 1 month
Weighted average remaining contractual term, options vested and expected to vest	6 years
Intrinsic value, outstanding	$ 89,300		$ 80,826
Intrinsic value, exercisable	77,650
Intrinsic value, options vested and expected to vest	$ 89,196