Summary of Significant Accounting Policies - Comprehensive Income (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Accumulated Other Comprehensive Income (Loss) [Line Items]
Component of accumulated other comprehensive income (loss), net of tax	$ (2,591)	$ 1,240
Unrealized gains (losses) on available-for-sale securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Component of accumulated other comprehensive income (loss), net of tax	(536)	3,295
Minimum pension liability adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Component of accumulated other comprehensive income (loss), net of tax	$ 2,055	$ 2,055