Summary of Significant Accounting Policies - Core Deposit Intangibles (Details) (Core Deposits Intangibles, USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Core Deposits Intangibles
Intangible Assets, Net (Excluding Goodwill) [Abstract]
Weighted average useful life of related deposits	9 years 6 months
Accumulated core deposit intangibles amortization	$ 20,983	$ 19,563
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
2013	1,417
2014	1,417
2015	1,417
2016	1,380
2017	$ 306