Income Taxes (Schedule of Effective Income Tax Reconciliation) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Tax at statutory rate	$ 70,406	$ 56,621	$ 49,599
State income taxes, net of federal tax benefits	6,627	4,641	5,132
Non-deductible meals and entertainment	1,687	1,497	1,577
Income tax credits	(1,700)	(1,600)	(1,574)
Other, net	427	1,965	192
Total income tax expense	$ 77,447	$ 63,124	$ 54,926