Net Deferred Tax Asset and Income Taxes (Schedule of Components of Income Tax Expense) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Current tax expense:
Federal	$ 13,937	$ 13,227	$ 10,576
State	533	558	414
Total current tax expense	14,470	13,785	10,990
Deferred tax expense (benefit):
Federal	1,310	(789)	(628)
State	18	(74)	(60)
Total deferred tax expense (benefit)	1,328	(863)	(688)
Total income tax expense	$ 15,798	$ 12,922	$ 10,302