Income Taxes (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2014	Mar. 31, 2014	Jun. 30, 2013	Mar. 31, 2013	Jun. 30, 2014	Jun. 30, 2013
Change in Accounting Estimate [Line Items]
Income tax expense	$ 6,034		$ 6,837		$ 10,501	$ 8,053
Effective tax rate	34.70%	33.10%	36.10%	29.50%
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)