Senior Notes - Summary of Fixed-Rate Senior Notes (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2012
Senior Notes [Line Items]
Redemption of notes	The Company may redeem the senior convertible notes any time on or after November 15, 2015, in whole or in part, for cash equal to 100% of the principal amount of the notes plus accrued and unpaid interest through, but excluding, the redemption date.