Income Taxes (Income Tax Reconciliation) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Income before provision for income taxes	$ 107,705	$ 82,279	$ 60,720
Federal income tax expense at statutory rate	37,697	28,798	21,252
Increases (decreases) resulting from:
State income taxes, net of federal income tax benefits	6,862	4,804	2,050
Impact of non-controlling interest	(2,516)	(4,290)	88
Non-deductible expenses	2,941	2,581	2,698
Impact of domestic production deduction	(3,436)	(248)	(1,889)
Tax credits	(265)	(275)	(433)
Other	152	0	0
Inclusion of tax liabilities from unincorporated entities	831	1,374	0
Changes in valuation allowance, net of equity and tax audit adjustments	(1,033)	421	(94)
Income tax expense	$ 41,233	$ 33,165	$ 23,672