Goodwill and Other Intangible Assets - Schedule of Changes in Carrying Amount of Goodwill (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended								6 Months Ended			6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014 Banking [Member]	Jun. 30, 2013 Banking [Member]	Jun. 30, 2014 Insurance [Member]	Dec. 31, 2013 Insurance [Member]	Jun. 30, 2013 Insurance [Member]	Dec. 31, 2012 Insurance [Member]	Jun. 30, 2014 Wealth Management [Member]	Jun. 30, 2013 Wealth Management [Member]	Dec. 31, 2012 Wealth Management [Member]	Jun. 30, 2014 Other [Member]	Jun. 30, 2013 Other [Member]
Goodwill [Line Items]
Beginning balance	$ 352,729	$ 338,820	$ 310,964	$ 297,055	$ 39,873	$ 39,873	$ 39,873	$ 39,873	$ 1,892	$ 1,892	$ 1,892
Goodwill acquired during the period	55,745	562	53,919	562					1,826
Ending balance	$ 408,474	$ 339,382	$ 364,883	$ 297,617	$ 39,873	$ 39,873	$ 39,873	$ 39,873	$ 3,718	$ 1,892	$ 1,892