Income Taxes - Provision (benefit) for income taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current Income Tax Expense (Benefit), Continuing Operations [Abstract]
Federal	$ 33,600	$ 42,600	$ 60,800
State	6,400	5,100	6,400
Foreign	2,100	2,900	2,300
Current Income Tax Expense	42,100	50,600	69,500
Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract]
Federal	(7,800)	(131,000)	(9,500)
State	(4,000)	(5,100)	(3,200)
Deferred income tax expense (benefit)	(11,847)	(136,127)	(12,714)
Provision (benefit) for income taxes	$ 30,254	$ (85,559)	$ 56,849