Common Stock - Additional Information (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended			168 Months Ended	240 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013	Dec. 31, 2013
Statement Of Stockholders Equity [Abstract]
Common shares outstanding	4,433,725	4,914,130		4,433,725	4,433,725
Treasury stock repurchases, shares	581,387	285,495	1,017,588		23,300,000
Treasury stock repurchases, value	$ 554,491	$ 227,281	$ 689,302		$ 5,308,000
Treasury stock reissued, shares				7,164,000
Reissued shares during the period, shares	101,850	221,992	333,380