Investment Securities - Available for Sale by Contractual Maturity (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Due in one year or less, Amortized cost	$ 21,105
Due after one year through five years, Amortized cost	76,516
Due after five years through ten years, Amortized cost	0
Due after ten years, Amortized cost	3,010
Amortized cost	1,128,221	1,162,332
Due in one year or less, Fair value	21,156
Due after one year through five years, Fair value	76,846
Due after five years through ten years, Fair value	0
Due after ten years , Fair value	2,958
Securities available for sale, at fair value	1,130,141	1,157,594
Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	1,027,193	1,060,013
Securities available for sale, at fair value	1,028,687	1,054,974
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	397	357
Securities available for sale, at fair value	$ 494	$ 446