Nature of Operations and Summary of Significant Accounting Policies - Recent Accounting Pronouncements (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Long-term deferred income taxes payable	$ 419,020	$ 565,404
Retained Earnings (Accumulated Deficit)	1,516,957	1,103,751
Accounting Standards Update 2016-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net deferred tax liabilities	900
Retained Earnings (Accumulated Deficit)	900
Income tax benefit	$ 5,400
Scenario, adjustment | Accounting Standards Update 2015-07
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net deferred tax liabilities		129,300
Long-term deferred income taxes payable		$ (129,300)