Investment Securities - Contractual Maturities of Debt Securities Held to Maturity (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Investments, Debt and Equity Securities [Abstract]
Due in one year, Amortized Cost	$ 80,902
Due after one year through five years, Amortized Cost	37,304
Due after five years through ten years, Amortized Cost	329,793
Due after ten years, Amortized Cost	359,058
Residential mortgage-backed securities, Amortized Cost	1,019,086
Total investment securities held to maturity, Amortized Cost	1,826,143	1,731,737
Due in one year, Fair Value	80,962
Due after one year through five years, Fair Value	42,340
Due after five years through ten years, Fair Value	346,954
Due after ten years, Fair Value	355,745
Residential mortgage-backed securities, Fair Value	1,028,120
Fair Value	$ 1,854,121	$ 1,711,427