Investment Securities - Contractual Maturities of Debt Securities Held to Maturity (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Investments Debt And Equity Securities [Abstract]
Due in one year, Amortized Cost	$ 129,999
Due after one year through five years, Amortized Cost	44,695
Due after five years through ten years, Amortized Cost	313,054
Due after ten years, Amortized Cost	357,946
Residential mortgage-backed securities, Amortized Cost	886,043
Total investment securities held to maturity, Amortized Cost	1,731,737	1,599,707
Due in one year, Fair Value	130,174
Due after one year through five years, Fair Value	49,102
Due after five years through ten years, Fair Value	320,966
Due after ten years, Fair Value	340,164
Residential mortgage-backed securities, Fair Value	871,021
Fair Value	$ 1,711,427	$ 1,657,950