Long-Term Debt - Summary of Long-Term Debt (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Debt Disclosure [Abstract]
Term Credit Agreement, Fair Value	$ 0	$ 100,000
Convertible Notes, Fair Value	346,130	332,003
Total, Fair Value	346,130	432,003
Less: Current portion recorded in Accrued expenses and other liabilities, Fair Value	0	50,000
Total Long-term debt, Fair Value	346,130	382,003
Term Credit Agreement, Carrying Amount	0	100,000
Convertible Notes, Carrying Amount	346,449	338,753
Total, Carrying Amount	346,449	438,753
Less: Current portion recorded in Accrued expenses and other liabilities, Carrying Amount	0	(50,000)
Total Long-term debt, Carrying Amount	$ 346,449	$ 388,753