Share-Based Payment Arrangements - Additional Information (Detail) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($) Bank $ / shares shares	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized stock-based compensation | $	$ 12,900	$ 14,000	$ 13,100
Recognized tax benefit related to the share-based compensation | $	$ 4,800	4,900	4,600
Percentage where a option price is equal to market price	110.00%
Term of option award vest, contractual term	10 years
Term of option award vest for continuous service	5 years
Intrinsic value of options exercised | $	$ 20	400	$ 600
Unrecognized compensation expense | $	$ 45,800
Weighted-average period in years	3 years 7 months 6 days
Total fair value of shares vested | $	$ 12,200	$ 12,800
Shareholder return period	3 years
Number of peer group of regional banks | Bank	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 | shares	59,312
Weighted average fair value of shares granted | $ / shares	$ 25.77
Percentage of maximum number of shares earned of target award	200.00%
2014 Long Term Incentive Plan [Member] | Stock Compensation Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of common shares can be granted under long term incentive Plan | shares	1,796,357
Shares available for future issuance under equity compensation plans | shares	1,300,000
Number of shares can be granted under long term incentive plan | shares	100,000
2010 Employee Stock Purchase Plan [Member] | Stock Compensation Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future issuance under equity compensation plans | shares	143,940