Condensed Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014
Statement of Comprehensive Income [Abstract]
Net income	$ 8,336us-gaap_NetIncomeLoss	$ 5,650us-gaap_NetIncomeLoss	$ 8,234us-gaap_NetIncomeLoss	$ 4,859us-gaap_NetIncomeLoss	$ 7,365us-gaap_NetIncomeLoss
Other comprehensive income (loss), net of tax:
Unrealized gains (losses) on available for sale securities arising during the period	9				(60)
Change in minimum pension liability	111				5
Other comprehensive income (loss)	120				(55)
Comprehensive income	$ 8,456us-gaap_ComprehensiveIncomeNetOfTax				$ 7,310us-gaap_ComprehensiveIncomeNetOfTax

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

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Amount after tax, before reclassification adjustments, of unrealized holding gain (loss) on available-for-sale securities.

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