Income Taxes - Deferred Portion of Tax Provision (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Amortization of franchise rights	$ 514	$ 514	$ 514
Amortization of other intangibles	1,590	1,241	621
Accrued expenses, deducted for tax when paid	(17,664)	(14,221)	(11,190)
Capitalized costs for books, deducted for tax	5,315	8,809	3,019
Depreciation	(5,932)	(4,147)	(2,597)
Federal impact of unrecognized tax benefits	1,058	44	(274)
Foreign tax credit carryforwards	3,636	(186)	(3,449)
Other, net	2,904	4,303	97
Deferred Portion Of Tax Expense Benefit, Total	$ (8,579)	$ (3,643)	$ (13,259)