Senior Note Due May 1, 2016 - Additional Information (Detail) (USD $)	0 Months Ended	3 Months Ended
	Oct. 04, 2013	Mar. 31, 2014	Mar. 31, 2013
Debt Instrument [Line Items]
Interest expense		$ 3,852,000	$ 2,051,000
Senior Notes
Debt Instrument [Line Items]
Unamortized discount		1,700,000
Interest expense		3,900,000
Senior Notes | 5.75% Senior Notes
Debt Instrument [Line Items]
Principal amount of senior notes	265,000,000
Interest rate stated on senior notes	5.75%
Senior notes due date	Oct. 15, 2023
Net proceeds from issuance of senior notes	263,000,000
Outstanding principal amount of senior notes		263,300,000
Fair value of senior notes		286,700,000
Effective interest rate related to senior notes		5.86%
Debt instrument, covenant compliance		As of March 31, 2014, the Company was in compliance with all such covenants.
Senior Notes | 5.75% Senior Notes | Semi Annual Payment, First Payment
Debt Instrument [Line Items]
Interest payment date on senior notes		--04-15
Senior Notes | 5.75% Senior Notes | Semi Annual Payment, Second Payment
Debt Instrument [Line Items]
Interest payment date on senior notes		--10-15
Senior Notes | 7.0 % Senior Notes
Debt Instrument [Line Items]
Interest rate stated on senior notes		7.00%
Senior notes due date		May 01, 2016
Call premium on redemption of Senior Notes	17,900,000
Interest expense on senior notes			$ 2,000,000