Income Taxes (Income Tax Reconciliation) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Income before income taxes	$ 126,429	$ 107,705	$ 82,279
Federal income tax expense at statutory rate	44,250	37,697	28,798
Increases (decreases) resulting from:
State income taxes, net of federal income tax benefits	6,991	6,862	4,804
Impact of non-controlling interest	(2,148)	(2,516)	(4,290)
Non-deductible expenses	2,569	2,941	2,581
Impact of domestic production deduction	(2,603)	(3,436)	(248)
Tax credits	(359)	(265)	(275)
Other	(1,202)	152	0
Inclusion of tax liabilities from unincorporated entities	1,126	831	1,374
Changes in valuation allowance, net of equity and tax audit adjustments	539	(1,033)	421
Income tax expense	$ 49,163	$ 41,233	$ 33,165