Summary of Significant Accounting Policies - Recent Accounting Pronouncements (Details) - USD ($) $ in Thousands	1 Months Ended
	Jan. 31, 2016	Jan. 01, 2019	Dec. 31, 2018	Dec. 31, 2017	Oct. 31, 2016
New Accounting Pronouncement, Early Adoption
Decrease in deferred tax asset			$ (345,091)	$ (419,003)
Accounting Standards Update 2016-16
New Accounting Pronouncement, Early Adoption
Decrease in deferred tax asset					$ 34,100
Accounting Standards Update 2016-01
New Accounting Pronouncement, Early Adoption
Adjustment to retained earnings	$ 9,100
Accounting Standards Update 2016-02 | Forecast
New Accounting Pronouncement, Early Adoption
Right of use assets		$ 30,000
Accounting Standards Update 2016-02 | Minimum | Forecast
New Accounting Pronouncement, Early Adoption
Lease liability		25,000
Right of use assets		25,000
Accounting Standards Update 2016-02 | Maximum | Forecast
New Accounting Pronouncement, Early Adoption
Lease liability		30,000
Right of use assets		$ 30,000