Fair Value of Assets and Liabilities - Schedule of Assets and Liabilities Measure at Fair Value (Details) - Recurring $ in Thousands	Mar. 31, 2018 USD ($)
Marketable securities
Recurring Fair Value Measurements:
Assets, fair value	$ 247,879
Quoted Prices in Active Markets for Identical Assets (Level 1) | Marketable securities
Recurring Fair Value Measurements:
Assets, fair value	247,879
Significant Other Observable Inputs (Level 2) | Marketable securities
Recurring Fair Value Measurements:
Assets, fair value	0
Significant Unobservable Inputs (Level 3) | Marketable securities
Recurring Fair Value Measurements:
Assets, fair value	0
Interest rate cap
Recurring Fair Value Measurements:
Assets, fair value	84
Interest rate cap | Quoted Prices in Active Markets for Identical Assets (Level 1)
Recurring Fair Value Measurements:
Assets, fair value	0
Interest rate cap | Significant Other Observable Inputs (Level 2)
Recurring Fair Value Measurements:
Assets, fair value	84
Interest rate cap | Significant Unobservable Inputs (Level 3)
Recurring Fair Value Measurements:
Assets, fair value	$ 0