Loans and Allowance - Changes in Allowance for Loan Losses by Loan Segment (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Allowance for loan losses:
Beginning balance				$ 69,366				$ 70,898	$ 69,366	$ 70,898	$ 82,977
Provision for losses	1,016	1,533	1,997	2,102	4,505	4,609	4,545	4,875	6,648	18,534	22,630
Recoveries on loans									9,990	7,206	13,764
Loans charged off									(18,134)	(27,272)	(48,473)
Ending balance	67,870				69,366				67,870	69,366	70,898
Commercial
Allowance for loan losses:
Beginning balance				25,913				17,731	25,913	17,731	32,508
Provision for losses									2,794	14,749	(13,787)
Recoveries on loans									4,586	1,744	8,828
Loans charged off									(6,117)	(8,311)	(9,818)
Ending balance	27,176				25,913				27,176	25,913	17,731
Commercial Real Estate
Allowance for loan losses:
Beginning balance				26,703				37,919	26,703	37,919	36,341
Provision for losses									340	(2,546)	28,574
Recoveries on loans									3,552	3,652	2,811
Loans charged off									(7,493)	(12,322)	(29,807)
Ending balance	23,102				26,703				23,102	26,703	37,919
Consumer
Allowance for loan losses:
Beginning balance				2,593				2,902	2,593	2,902	3,622
Provision for losses									(11)	126	(221)
Recoveries on loans									556	695	942
Loans charged off									(623)	(1,130)	(1,441)
Ending balance	2,515				2,593				2,515	2,593	2,902
Residential
Allowance for loan losses:
Beginning balance				14,157				12,343	14,157	12,343	10,408
Provision for losses									3,514	6,176	8,166
Recoveries on loans									1,292	1,113	1,176
Loans charged off									(3,886)	(5,475)	(7,407)
Ending balance	15,077				14,157				15,077	14,157	12,343
Finance Leases
Allowance for loan losses:
Beginning balance								3		3	98
Provision for losses									11	29	(102)
Recoveries on loans									4	2	7
Loans charged off									(15)	(34)
Ending balance											$ 3