Summary of Significant Accounting Policies (Details 2) (USD $)	3 Months Ended	12 Months Ended
Mar. 31, 2013 item	Mar. 31, 2012	Dec. 31, 2012
Stock-Based Compensation
Stock-based compensation expense	$ 873,000	$ 378,000
Stock-based compensation expense, net of tax	536,000	249,000
Unrecognized compensation cost	10,700,000
Unrecognized compensation cost, weighted-average period for recognition	3 years 8 months 12 days
Stock-based compensation costs capitalized as part of cost of asset	0		0
Comprehensive Income
Cumulative other comprehensive income, net of tax	$ 816,000		$ 549,000
Segments of an Enterprise and Related Information
Number of operating segments	1

Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge.

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