Segment Information - Results of Operations and Selected Financial Information (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
Segment Reporting Information [Line Items]
Net interest income (expense)	$ 41,921	$ 40,712	$ 40,630	$ 40,256	$ 42,297	$ 40,832	$ 40,869	$ 40,817	$ 163,519	$ 164,815	$ 156,897
Provision for loan losses	454	(12)	516	300	2,446	233	248	173	1,258	3,100	4,515
Noninterest income	22,235	23,652	21,733	22,535	21,800	22,116	20,364	23,437	90,155	87,717	76,961
Depreciation and amortization									11,077	10,840	9,682
Other expenses									160,497	159,588	148,964
Income before taxes									80,842	79,004	70,697
Total assets	6,038,974				6,022,250				6,038,974	6,022,250	5,608,825
Capital expenditures									13,896	13,438	16,380
Operating Segments [Member] | Metropolitan Banks [Member]
Segment Reporting Information [Line Items]
Net interest income (expense)									56,346	54,062	50,952
Provision for loan losses									(154)	1,202	21
Noninterest income									12,881	11,222	11,226
Depreciation and amortization									2,178	1,956	1,733
Other expenses									31,396	29,511	29,527
Income before taxes									35,807	32,615	30,897
Total assets	2,079,444				1,996,539				2,079,444	1,996,539	1,738,426
Capital expenditures									5,534	4,099	2,265
Operating Segments [Member] | Community Banks [Member]
Segment Reporting Information [Line Items]
Net interest income (expense)									102,705	105,966	102,528
Provision for loan losses									1,205	1,607	4,205
Noninterest income									48,418	43,809	39,529
Depreciation and amortization									7,011	6,898	6,128
Other expenses									84,011	80,535	74,527
Income before taxes									58,896	60,735	57,197
Total assets	3,764,429				3,801,653				3,764,429	3,801,653	3,660,239
Capital expenditures									6,445	8,045	12,561
Operating Segments [Member] | Other Financial Services [Member]
Segment Reporting Information [Line Items]
Net interest income (expense)									6,239	7,055	7,055
Provision for loan losses									121	182	276
Noninterest income									25,659	29,624	23,148
Depreciation and amortization									521	485	505
Other expenses									21,604	22,056	19,569
Income before taxes									9,652	13,956	9,853
Total assets	103,656				186,473				103,656	186,473	153,872
Capital expenditures									219	398	107
Operating Segments [Member] | Executive, Operations and Support [Member]
Segment Reporting Information [Line Items]
Net interest income (expense)									(1,771)	(2,268)	(3,638)
Provision for loan losses									86	109	13
Noninterest income									59,298	56,848	51,144
Depreciation and amortization									1,367	1,501	1,316
Other expenses									23,818	27,783	25,627
Income before taxes									32,256	25,187	20,550
Total assets	703,294				602,342				703,294	602,342	602,577
Capital expenditures									1,698	896	1,447
Eliminations [Member]
Segment Reporting Information [Line Items]
Net interest income (expense)
Provision for loan losses
Noninterest income									(56,101)	(53,786)	(48,086)
Depreciation and amortization
Other expenses									(332)	(297)	(286)
Income before taxes									(55,769)	(53,489)	(47,800)
Total assets	(611,849)				(564,757)				(611,849)	(564,757)	(546,289)
Capital expenditures