Investment Securities - Summary of Gains or Losses on Proceeds from Maturities, Sales and Calls of Available for Sale Securities by Specific Identification Method (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Investments Debt And Equity Securities [Abstract]
Proceeds from maturities, sales and calls	$ 698,264	$ 1,996,547	$ 1,486,936
Gross realized gains	1,259	157	1,729
Gross realized losses	$ 43	$ 141	$ 311