Segment Information - Results of Operations and Selected Financial Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Segment Reporting Information [Line Items]
Net interest income (expense)	$ 40,630	$ 40,869	$ 80,886	$ 81,686
Noninterest income	21,733	20,364	44,268	43,801
Income before taxes	19,392	18,422	39,939	40,466
Total Assets	5,749,666	5,671,711	5,749,666	5,671,711	6,022,250
Metropolitan Banks [Member]
Segment Reporting Information [Line Items]
Net interest income (expense)	13,943	13,354	27,954	26,517
Noninterest income	3,116	2,672	6,306	5,353
Income before taxes	8,108	8,220	17,045	16,652
Total Assets	1,945,032	1,801,752	1,945,032	1,801,752	1,996,539
Community Banks [Member]
Segment Reporting Information [Line Items]
Net interest income (expense)	25,424	26,384	50,568	53,015
Noninterest income	11,846	10,721	23,391	20,856
Income before taxes	14,512	14,944	28,589	30,199
Total Assets	3,590,420	3,688,931	3,590,420	3,688,931	3,801,653
Other Financial Services [Member]
Segment Reporting Information [Line Items]
Net interest income (expense)	1,730	1,721	3,295	3,434
Noninterest income	6,073	6,214	12,975	16,078
Income before taxes	2,158	2,011	5,395	8,398
Total Assets	93,047	130,762	93,047	130,762	186,473
Executive, Operations and Support [Member]
Segment Reporting Information [Line Items]
Net interest income (expense)	(467)	(590)	(931)	(1,280)
Noninterest income	13,792	13,245	28,541	28,626
Income before taxes	7,643	5,686	15,737	12,219
Total Assets	706,501	607,662	706,501	607,662	602,342
Eliminations [Member]
Segment Reporting Information [Line Items]
Net interest income (expense)
Noninterest income	(13,094)	(12,488)	(26,945)	(27,112)
Income before taxes	(13,029)	(12,439)	(26,827)	(27,002)
Total Assets	$ (585,334)	$ (557,396)	$ (585,334)	$ (557,396)	$ (564,757)