Changes in Shareholders' Equity - Changes in Shareholders' Equity (Parenthetical) (Detail) shares in Thousands	6 Months Ended
	Jun. 30, 2016 $ / shares shares
Issuance of common shares for stock options exercised | shares	1,905
Preferred stock dividends per share	$ 5.00
Common stock dividends per share	$ 0.04
Common Stock [Member]
Issuance of common shares for stock options exercised | shares	1,905
Additional Paid-in Capital [Member]
Issuance of common shares for stock options exercised | shares	1,905
Retained Earnings [Member]
Preferred stock dividends per share	$ 5.00
Common stock dividends per share	$ 0.04