Equity Transactions - Additional Information (Detail) (USD $)	12 Months Ended			9 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	May 31, 2013	Sep. 30, 2013 Public Offering [Member]
Equity, Class of Treasury Stock [Line Items]
Common stock, shares issued				1,300,000
Common stock value	$ 191,578,000			$ 191,800,000
Treasury stock, shares acquired	105,000	90,000
Weighted average purchase price per share	$ 187.61	$ 99.30
Total cost of treasury shares acquired	19,700,000	8,900,000
Treasury stock, shares	350,000	245,000
Treasury stock, at cost	$ 37,438,000	$ 17,734,000
Repurchased additional shares of common stock, shares			350,000
Common stock remaining authorized for repurchase	350,000
Repurchase program expiration date	May 21, 2016