Goodwill and Other Intangible Assets - Carrying Amount of Goodwill (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2012
Goodwill [Roll Forward]
Beginning balance	$ 428,234	$ 428,234
Goodwill from business combinations	147,658
Ending balance	575,892	428,234
Wealth Management [Member]
Goodwill [Roll Forward]
Beginning balance	20,517	20,517
Goodwill from business combinations	0
Ending balance	20,517	20,517
Consumer Lending [Member]
Goodwill [Roll Forward]
Beginning balance	128,451	128,451
Goodwill from business combinations	40,471
Ending balance	168,922	128,451
Commercial Lending
Goodwill [Roll Forward]
Beginning balance	174,763	174,763
Goodwill from business combinations	78,137
Ending balance	252,900	174,763
Investment Management
Goodwill [Roll Forward]
Beginning balance	104,503	104,503
Goodwill from business combinations	29,050
Ending balance	$ 133,553	$ 104,503