Allowance For Loan Losses And Recorded Investment In Loans By Portfolio Segment And Based On Impairment Method (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Mar. 31, 2012
Allowance for loan losses:
Associated with impaired loans	$ 29,092	$ 44,150
Associated with all other loans	50,723	67,065
Total	79,815	111,215
Loans:
Impaired loans individually evaluated	160,355	297,572
All other loans	1,602,841	1,890,511
Total	1,763,196	2,188,083
Commercial Real Estate
Allowance for loan losses:
Associated with impaired loans	19,182	33,137
Associated with all other loans	35,399	52,016
Total	54,581	85,153
Loans:
Impaired loans individually evaluated	114,540	228,873
All other loans	656,403	845,943
Total	770,943	1,074,816
Consumer
Allowance for loan losses:
Associated with impaired loans	364	385
Associated with all other loans	3,273	2,082
Total	3,637	2,467
Loans:
Impaired loans individually evaluated	4,677	8,514
All other loans	409,282	501,349
Total	413,959	509,863
Residential
Allowance for loan losses:
Associated with impaired loans	7,038	5,080
Associated with all other loans	7,487	7,947
Total	14,525	13,027
Loans:
Impaired loans individually evaluated	37,378	49,411
All other loans	510,342	515,016
Total	547,720	564,427
Commercial and industrial
Allowance for loan losses:
Associated with impaired loans	2,508	5,548
Associated with all other loans	4,564	5,020
Total	7,072	10,568
Loans:
Impaired loans individually evaluated	3,760	10,774
All other loans	26,814	28,203
Total	$ 30,574	$ 38,977