Income Taxes (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Change in Accounting Estimate [Line Items]
Income tax expense	$ 7,092	$ 6,482	$ 17,593	$ 14,535
Effective tax rate	36.30%	38.10%	34.30%	32.80%
Expected effective income tax rate for the year			34.00%
Statutory federal tax rate			35.00%
Investment Tax Credit Carryforward [Member]
Change in Accounting Estimate [Line Items]
Income tax expense			$ (700)