Debt - Interest Rate Swaps (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) outstanding_contract	Dec. 31, 2018 USD ($) derivative_instrument outstanding_contract	Dec. 31, 2016 USD ($)
Derivative [Line Items]
Number of Contracts | outstanding_contract	142	142
Contract notional amount	$ 2,086,764	$ 3,027,375
Interest rate swap
Derivative [Line Items]
Number of Contracts | derivative_instrument		5
Contract notional amount		$ 1,400,000
Derivative, term of contract	30 days
Interest rate derivative hedge, asset (liability), net	$ 10,700		$ (3,400)
Forward starting interest rate swap
Derivative [Line Items]
Number of Contracts | derivative_instrument		2
Contract notional amount		$ 700,000
Minimum | Interest rate swap
Derivative [Line Items]
Derivative, fixed interest rate	1.53%
Maximum | Interest rate swap
Derivative [Line Items]
Derivative, fixed interest rate	2.13%