Shareholders' Equity - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Cash dividends declared on common shares, per share	$ 0.075	$ 0.065	$ 0.215	$ 0.185
Dividend payable			$ 199,000,000	$ 178,000,000
Series A Preferred Stock [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Dividend payable per share	$ 1.9375		$ 1.9375
Dividend payable	$ 5,600,000
2015 Capital Plan [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Repurchase of common stock	725,000,000		$ 725,000,000
Stock repurchase program authorized amount	$ 123,000,000
Cash dividends declared on common shares, per share	$ 0.075
2016 [Member] | 2015 Capital Plan [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Proposed increase in cash dividends declared on common shares, per share			$ 0.085