Securities - Held to Maturity with Unrealized Losses (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Schedule of Held-to-maturity Securities [Line Items]
Held to maturity securities, Losses less than 12 months, Fair Value	$ 207,129	$ 2,028,848
Held to maturity securities, Losses Less than 12 months, Gross Unrealized Losses	2,457	36,070
Held to maturity securities, Losses 12 months or longer, Fair value	844,193	178,511
Held to maturity securities, Losses 12 months or longer, Gross Unrealized Losses	13,475	1,291
Held to maturity securities, Total, Fair value	1,051,322	2,207,359
Held to maturity securities, Total, Gross Unrealized Losses	15,932	37,361
Municipal obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held to maturity securities, Losses less than 12 months, Fair Value	495	131,499
Held to maturity securities, Losses Less than 12 months, Gross Unrealized Losses	5	6,311
Held to maturity securities, Losses 12 months or longer, Fair value	60,099	2,878
Held to maturity securities, Losses 12 months or longer, Gross Unrealized Losses	1,917	125
Held to maturity securities, Total, Fair value	60,594	134,377
Held to maturity securities, Total, Gross Unrealized Losses	1,922	6,436
Mortgage-backed securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held to maturity securities, Losses less than 12 months, Fair Value		950,288
Held to maturity securities, Losses Less than 12 months, Gross Unrealized Losses		4,671
Held to maturity securities, Losses 12 months or longer, Fair value	134,550
Held to maturity securities, Losses 12 months or longer, Gross Unrealized Losses	693
Held to maturity securities, Total, Fair value	134,550	950,288
Held to maturity securities, Total, Gross Unrealized Losses	693	4,671
Collateralized mortgage obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held to maturity securities, Losses less than 12 months, Fair Value	206,634	947,061
Held to maturity securities, Losses Less than 12 months, Gross Unrealized Losses	2,452	25,088
Held to maturity securities, Losses 12 months or longer, Fair value	649,544	175,633
Held to maturity securities, Losses 12 months or longer, Gross Unrealized Losses	10,865	1,166
Held to maturity securities, Total, Fair value	856,178	1,122,694
Held to maturity securities, Total, Gross Unrealized Losses	$ 13,317	$ 26,254