Summary of Significant Accounting Policies - Core Deposit Intangibles (Details) (Core Deposits Intangibles, USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Core Deposits Intangibles
Intangible Assets, Net (Excluding Goodwill) [Abstract]
Accumulated core deposit intangibles amortization	$ 24,652	$ 22,401
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
2015	3,336
2016	3,099
2017	1,825
2018	1,318
2019	1,118
Thereafter	$ 2,587