Past Due Loans, Allowances For Credit Losses, Impaired Loans, and TDRs (Detail) - Allowance for Credit Losses (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at the beginning of the year	$ 87,121	$ 102,812	$ 121,962
Charge-offs	(40,184)	(38,580)	(182,807)
Recoveries	8,205	8,382	5,605
Net charge-offs	(31,979)	(30,198)	(177,202)
Provision for loan and covered loan losses	19,368	14,507	158,052
Balance at the end of the year	74,510	87,121	102,812
Commercial Industrial And Agricultural
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at the beginning of the year	30,381	36,761	46,017
Charge-offs	(17,424)	(12,094)	(64,668)
Recoveries	3,800	3,797	3,393
Net charge-offs	(13,624)	(8,297)	(61,275)
Provision for loan and covered loan losses	12,701	1,917	52,019
Balance at the end of the year	29,458	30,381	36,761
Office Retail And Industrial
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at the beginning of the year	10,405	11,432	16,012
Charge-offs	(7,345)	(4,744)	(34,968)
Recoveries	497	228	577
Net charge-offs	(6,848)	(4,516)	(34,391)
Provision for loan and covered loan losses	7,435	3,489	29,811
Balance at the end of the year	10,992	10,405	11,432
Multi-Family
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at the beginning of the year	2,017	3,575	5,067
Charge-offs	(943)	(1,029)	(3,361)
Recoveries	87	584	275
Net charge-offs	(856)	(445)	(3,086)
Provision for loan and covered loan losses	1,088	(1,113)	1,594
Balance at the end of the year	2,249	2,017	3,575
Construction
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at the beginning of the year	6,316	9,223	17,795
Charge-offs	(1,052)	(1,916)	(27,811)
Recoveries	166	1,032	451
Net charge-offs	(886)	(884)	(27,360)
Provision for loan and covered loan losses	(3,133)	(2,023)	18,788
Balance at the end of the year	2,297	6,316	9,223
Other Commerical Real Estate
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at the beginning of the year	10,817	13,531	19,451
Charge-offs	(4,834)	(4,784)	(36,474)
Recoveries	1,727	1,646	125
Net charge-offs	(3,107)	(3,138)	(36,349)
Provision for loan and covered loan losses	617	424	30,429
Balance at the end of the year	8,327	10,817	13,531
Consumer
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at the beginning of the year	13,010	12,862	14,131
Charge-offs	(7,574)	(9,414)	(10,910)
Recoveries	729	1,071	784
Net charge-offs	(6,845)	(8,343)	(10,126)
Provision for loan and covered loan losses	5,980	8,491	8,857
Balance at the end of the year	12,145	13,010	12,862
Covered Loans
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at the beginning of the year	12,559	12,062	989
Charge-offs	(1,012)	(4,599)	(4,615)
Recoveries	1,199	24	0
Net charge-offs	187	(4,575)	(4,615)
Provision for loan and covered loan losses	(5,520)	5,072	15,688
Balance at the end of the year	7,226	12,559	12,062
Reservefor Unfunded Commitments
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at the beginning of the year	1,616	3,366	2,500
Charge-offs	0	0	0
Recoveries	0	0	0
Net charge-offs	0	0	0
Provision for loan and covered loan losses	200	(1,750)	866
Balance at the end of the year	$ 1,816	$ 1,616	$ 3,366