Income Taxes (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Effective income tax	(17.80%)	(37.90%)	(26.60%)	(34.70%)
Deferred tax assets, net	$ 986,787		$ 986,787		$ 1,049,408
Gross unrecognized tax benefits	9,800		9,800		21,500
Accrued interest and penalties on unrecognized tax benefits	2,200		2,200		12,200
Possible decrease in unrecognized tax benefits	$ 6,400		$ 6,400
New Accounting Pronouncement, Early Adoption, Effect | Retained Earnings | Accounting Standards Update 2016-09, Excess Tax Benefit Component
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred income tax assets, net					$ 18,600