Components of Carrying Value of AFS Securities in Unrealized Loss Position (Detail) (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Consecutive Months Total Amortized Cost	$ 133,584	$ 106,288
Less Than 12 Consecutive Months Gross Unrealized Losses	(4,179)	(1,885)
Less Than 12 Consecutive Months Total Fair Value	129,405	104,403
12 Consecutive Months or Longer Total Amortized Cost	63,913	40,669
12 Consecutive Months or Longer Gross Unrealized Losses	(10,183)	(15,484)
12 Consecutive Months or Longer Total Fair Value	53,730	25,185
Residential
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Consecutive Months Total Amortized Cost	133,317	104,154
Less Than 12 Consecutive Months Gross Unrealized Losses	(4,100)	(1,628)
Less Than 12 Consecutive Months Total Fair Value	129,217	102,526
12 Consecutive Months or Longer Total Amortized Cost	61,687	26,374
12 Consecutive Months or Longer Gross Unrealized Losses	(9,420)	(6,778)
12 Consecutive Months or Longer Total Fair Value	52,267	19,596
Commercial
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Consecutive Months Total Amortized Cost	267	2,134
Less Than 12 Consecutive Months Gross Unrealized Losses	(79)	(257)
Less Than 12 Consecutive Months Total Fair Value	188	1,877
12 Consecutive Months or Longer Total Amortized Cost	2,226	1,728
12 Consecutive Months or Longer Gross Unrealized Losses	(763)	(384)
12 Consecutive Months or Longer Total Fair Value	1,463	1,344
CDO
Schedule of Available-for-sale Securities [Line Items]
12 Consecutive Months or Longer Total Amortized Cost		12,567
12 Consecutive Months or Longer Gross Unrealized Losses		(8,322)
12 Consecutive Months or Longer Total Fair Value		$ 4,245