Incentive Plans - Schedule of Issuance of RSUs and Charges to Retained Earnings (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of RSUs issued	442,242	920,791	389,846
Charges to retained earnings, net of estimated forfeitures	$ 16,476	$ 24,990	$ 11,120