Benefit Plans - Stock Options Activity (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Shares, Outstanding at beginning of year	1,828,591	2,322,593	2,860,081
Shares, Assumed in acquisition	100,000	0	0
Shares, Forfeited or expired	(545,226)	(494,002)	(537,488)
Shares, Outstanding at end of year	1,383,365	1,828,591	2,322,593
Shares, Exercisable at year-end	1,283,365	1,828,591	2,320,696
Weighted Average Exercise Price, Outstanding at beginning of year (in usd per share)	$ 17	$ 17	$ 17
Weighted Average Exercise Price, Assumed in acquisition (in usd per share)	11	0	0
Weighted Average Exercise Price, Forfeited or expired (in usd per share)	18	19	19
Weighted Average Exercise Price, Outstanding at end of year (in usd per share)	16	17	17
Weighted Average Exercise Price, Exercisable at year-end (in usd per share)	$ 16	$ 17	$ 17