Revenue - Remaining Performance Obligations (Details) $ in Thousands	Sep. 30, 2018 USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total net revenues	$ 1,836,150
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-10-01 | Subscription [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total net revenues	317,356
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-10-01 | Support and Services [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total net revenues	1,518,794
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total net revenues	86,251
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01 | Subscription [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total net revenues	30,371
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01 | Support and Services [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total net revenues	55,880
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total net revenues	806
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01 | Subscription [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total net revenues	526
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01 | Support and Services [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total net revenues	280
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total net revenues	1,923,207
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil) | Subscription [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total net revenues	348,253
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil) | Support and Services [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total net revenues	$ 1,574,954