Loans - Loans, Net of Unearned Income (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Aggregate Loans Receivable Including Loans Covered Under Loss Share Agreements [Line Items]
Total commercial	$ 4,433,288	$ 3,800,230
Total construction	989,306	1,263,005
Total real estate	2,923,094	2,998,923
Total residential mortgage loans	1,577,944	1,507,498
Total consumer loans	1,654,170	1,607,370
Total Loans	11,577,802	11,177,026
Originated loans [Member]
Aggregate Loans Receivable Including Loans Covered Under Loss Share Agreements [Line Items]
Total commercial	2,713,385	1,525,409
Total construction	665,673	540,806
Total real estate	1,548,402	1,259,757
Total residential mortgage loans	827,985	487,147
Total consumer loans	1,351,776	1,074,611
Total Loans	7,107,221	4,887,730
Acquired loans [Member]
Aggregate Loans Receivable Including Loans Covered Under Loss Share Agreements [Line Items]
Total commercial	1,690,643	2,236,758
Total construction	295,151	603,371
Total real estate	1,279,546	1,656,515
Total residential mortgage loans	486,444	734,669
Total consumer loans	202,974	386,540
Total Loans	3,954,758	5,617,853
Covered loans [Member]
Aggregate Loans Receivable Including Loans Covered Under Loss Share Agreements [Line Items]
Total commercial	29,260	38,063
Total construction	28,482	118,828
Total real estate	95,146	82,651
Total residential mortgage loans	263,515	285,682
Total consumer loans	99,420	146,219
Total Loans	$ 515,823	$ 671,443