Investment Securities (Investment Securities, Continuous Unrealized Loss Position, Fair Value) (Detail) $ in Thousands	Sep. 30, 2016 USD ($)
Schedule of Available-for-sale Securities [Line Items]
Continuous unrealized losses existing for less than 12 months, Fair value	$ 77,057
Continuous unrealized losses existing for less than 12 months, Unrealized losses	(592)
Continuous unrealized losses existing for greater than 12 months, Fair value	62,721
Continuous unrealized losses existing for greater than 12 months, Unrealized losses	(1,847)
Total, Fair value	139,778
Total, Unrealized losses	(2,439)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	252,325
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Unrealized Losses	(3,083)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	9,239
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Unrealized Losses	(110)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value	261,564
Held-to-maturity Securities, Continuous Unrealized Loss Position, Unrealized Losses	(3,193)
U.S. Treasury
Schedule of Available-for-sale Securities [Line Items]
Continuous unrealized losses existing for less than 12 months, Fair value	0
Continuous unrealized losses existing for less than 12 months, Unrealized losses	0
Continuous unrealized losses existing for greater than 12 months, Fair value	0
Continuous unrealized losses existing for greater than 12 months, Unrealized losses	0
Total, Fair value	0
Total, Unrealized losses	0
U.S. Government agencies
Schedule of Available-for-sale Securities [Line Items]
Continuous unrealized losses existing for less than 12 months, Fair value	35,173
Continuous unrealized losses existing for less than 12 months, Unrealized losses	(41)
Continuous unrealized losses existing for greater than 12 months, Fair value	0
Continuous unrealized losses existing for greater than 12 months, Unrealized losses	0
Total, Fair value	35,173
Total, Unrealized losses	(41)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	240,400
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Unrealized Losses	(2,879)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Unrealized Losses	0
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value	240,400
Held-to-maturity Securities, Continuous Unrealized Loss Position, Unrealized Losses	(2,879)
Municipal
Schedule of Available-for-sale Securities [Line Items]
Continuous unrealized losses existing for less than 12 months, Fair value	13,062
Continuous unrealized losses existing for less than 12 months, Unrealized losses	(45)
Continuous unrealized losses existing for greater than 12 months, Fair value	7,766
Continuous unrealized losses existing for greater than 12 months, Unrealized losses	(102)
Total, Fair value	20,828
Total, Unrealized losses	(147)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	11,925
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Unrealized Losses	(204)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	9,239
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Unrealized Losses	(110)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value	21,164
Held-to-maturity Securities, Continuous Unrealized Loss Position, Unrealized Losses	(314)
Corporate notes, Financial issuers
Schedule of Available-for-sale Securities [Line Items]
Continuous unrealized losses existing for less than 12 months, Fair value	10,000
Continuous unrealized losses existing for less than 12 months, Unrealized losses	(1)
Continuous unrealized losses existing for greater than 12 months, Fair value	34,650
Continuous unrealized losses existing for greater than 12 months, Unrealized losses	(1,310)
Total, Fair value	44,650
Total, Unrealized losses	(1,311)
Corporate notes, Other
Schedule of Available-for-sale Securities [Line Items]
Continuous unrealized losses existing for less than 12 months, Fair value	0
Continuous unrealized losses existing for less than 12 months, Unrealized losses	0
Continuous unrealized losses existing for greater than 12 months, Fair value	0
Continuous unrealized losses existing for greater than 12 months, Unrealized losses	0
Total, Fair value	0
Total, Unrealized losses	0
Mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Continuous unrealized losses existing for less than 12 months, Fair value	1,017
Continuous unrealized losses existing for less than 12 months, Unrealized losses	(22)
Continuous unrealized losses existing for greater than 12 months, Fair value	4,019
Continuous unrealized losses existing for greater than 12 months, Unrealized losses	(32)
Total, Fair value	5,036
Total, Unrealized losses	(54)
Mortgage-backed, Collateralized mortgage obligations
Schedule of Available-for-sale Securities [Line Items]
Continuous unrealized losses existing for less than 12 months, Fair value	1,255
Continuous unrealized losses existing for less than 12 months, Unrealized losses	(2)
Continuous unrealized losses existing for greater than 12 months, Fair value	7,499
Continuous unrealized losses existing for greater than 12 months, Unrealized losses	(100)
Total, Fair value	8,754
Total, Unrealized losses	(102)
Equity securities
Schedule of Available-for-sale Securities [Line Items]
Continuous unrealized losses existing for less than 12 months, Fair value	16,550
Continuous unrealized losses existing for less than 12 months, Unrealized losses	(481)
Continuous unrealized losses existing for greater than 12 months, Fair value	8,787
Continuous unrealized losses existing for greater than 12 months, Unrealized losses	(303)
Total, Fair value	25,337
Total, Unrealized losses	$ (784)