Income Taxes - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Summary Of Income Taxes [Line Items]
Expected provision at federal statutory tax rate		35.00%	35.00%	35.00%
Reduction in net deferred tax liabilities		$ 196,000
Income tax deficiency		500
Alternative minimum tax		6,300
Valuation allowance		454	$ 0
Foreign tax credits		6,000
State net operating losses		14,800
Excess tax (deficiency) benefit from equity-based compensation		$ 0	$ (470)	$ 8,850
Forecast
Summary Of Income Taxes [Line Items]
Expected provision at federal statutory tax rate	21.00%