Entry into Merger Agreement - Additional Information (Detail) (Kohlberg Kravis Roberts Co L P, USD $) In Millions, except Per Share data, unless otherwise specified			1 Months Ended
	Mar. 07, 2013	Mar. 31, 2013 If the Company terminates the merger agreement	Mar. 31, 2013 If the Company terminates the merger agreement Maximum	Mar. 31, 2013 If KKR terminates the merger agreement
Business Acquisition [Line Items]
Definitive merger agreement, acquisition price per share for outstanding common stock shares	$ 76.00
Merger agreement termination fee		$ 103.4		$ 263.1
Merger agreement, reimbursement expense in case of termination			$ 10