Investment Securities - Contractual Maturities of Debt Securities Held to Maturity (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Investments, Debt and Equity Securities [Abstract]
Due in one year, Amortized Cost	$ 102,621
Due after one year through five years, Amortized Cost	47,620
Due after five years through ten years, Amortized Cost	324,602
Due after ten years, Amortized Cost	366,892
Residential mortgage-backed securities, Amortized Cost	971,361
Total investment securities held to maturity, Amortized Cost	1,813,096	1,731,737
Due in one year, Fair Value	102,674
Due after one year through five years, Fair Value	52,243
Due after five years through ten years, Fair Value	337,343
Due after ten years, Fair Value	357,739
Residential mortgage-backed securities, Fair Value	966,050
Fair Value	$ 1,816,049	$ 1,711,427