Share-Based Payment Arrangements - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014 Bank	Mar. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Intrinsic value of options exercised	$ 0.2	$ 0.1
Unrecognized compensation cost	38.3
Weighted-average period in years	3 years 6 months
Total fair value of shares vested	$ 0.8	$ 0.5
Shareholder return period	3 years
Number of peer group of regional banks	50
Performance Share Award [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted to key members of executives and senior management	71,382
Weighted average fair value of shares granted	$ 38.11
Percentage of maximum number of shares earned of target award	200.00%