Stockholders’ Equity - Narrative (Details)	12 Months Ended	72 Months Ended
	Sep. 30, 2018 category item shares	Sep. 30, 2018 shares
Stockholders' Equity
Vesting period	3 years
RSUs
Stockholders' Equity
Number of units awarded (in shares)		2,262,340
Number of shares of common stock that each award holder has the contingent right to receive	1
Vested awards to date	645,989	645,989
Expected awards vested (in shares)	448,548
Time-based RSUs
Stockholders' Equity
Number of units awarded (in shares)		1,089,876
Number of equal installments for vesting of stock awards | item	4
Performance-based RSUs
Stockholders' Equity
Number of units awarded (in shares)		1,172,464
Vesting period	3 years
Number of vesting criteria which have to be satisfied out of total vesting criteria | category	1
Number of vesting criteria | category	3