Share-Based Compensation - Summary of Stock Option Activity under Plan (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Options outstanding
Options outstanding, beginning of period	331,174	411,794	438,394
Granted	0	0	0
Exercised	(250)
Forfeited		(15,250)	(4,200)
Expired	(125,950)	(65,370)	(22,400)
Options outstanding, end of period	204,974	331,174	411,794
Options exercisable, end of period	204,974	318,279	378,004
Options unvested, end of period		12,895	33,790
Options exercisable, end of period	204,974	318,279	378,004
Options unvested, end of period		12,895	33,790
Options outstanding, weighted average exercise price
Options outstanding, beginning of period	$ 39.37	$ 39.04	$ 38.76
Granted	$ 0	$ 0	$ 0
Exercised	$ 46.20
Forfeited		$ 42.45	$ 35.54
Expired	$ 48.21	$ 36.56	$ 34.25
Options outstanding, end of period	$ 33.94	$ 39.37	$ 39.04
Options exercisable, end of period	$ 33.94	$ 40.62	$ 41.00
Options unvested, end of period		$ 8.64	$ 17.17
Options outstanding
Options outstanding, end of period	2 years 4 months 24 days	2 years 2 months 12 days	2 years 9 months 18 days
Options exercisable, end of period	2 years 4 months 24 days	2 years 1 month 6 days	2 years 6 months
Options unvested, end of period	0 years	5 years	5 years 4 months 24 days
Options outstanding, end of period, aggregate intrinsic value
Options outstanding, end of period	$ 531	$ 1,708	$ 766
Options exercisable, end of period	531	1,373	459
Options unvested, end of period		$ 335	$ 307