Income Taxes - Deferred Portion of Tax Provision (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Accrued expenses, deducted for tax when paid	$ (17,797)	$ (21,884)	$ 15,213
Capitalized costs for books, deducted for tax	3,246	(4,832)	(5,790)
Depreciation	3,526	10,071	(4,079)
Tax effects of TCJA	0	0	34,633
Other, net	2,153	766	1,835
Deferred portion of the tax provision (benefit)	$ (8,872)	$ (15,879)	$ 41,812