Debt - Term Loan Facility Due Twenty Sixteen and Revolving Credit Facility - Additional Information (Details) (USD $)	3 Months Ended		1 Months Ended	3 Months Ended	1 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 20, 2011 Term Loan	Mar. 31, 2014 Term Loan	Dec. 20, 2011 Revolving Credit Facility	Mar. 31, 2014 Letter of Credit	Mar. 31, 2014 Borrowings On Same Day Notice
Debt Instrument [Line Items]
Maximum borrowing limits			$ 600,000,000
Term Loan Facility, principal amount	330,000,000		400,000,000
Period of Term Loan Facility			5 years		5 years
Borrowings, maturity date			Dec. 31, 2016		Dec. 31, 2016
Borrowing capacity under Revolving Credit Facility					200,000,000	40,000,000	40,000,000
Borrowings, interest rate description				Interest at LIBOR plus 150 basis points, or the Eurocurrency Spread, or the alternate base rate (“ABR”) plus 50 basis points
Borrowings alternate base rate	0.50%			1.50%
Commitment fee on undrawn amount	0.225%
Borrowings, interest rate basis				1.70%
Principal repayment of term loan				2.50%
Principal payments on long-term debt	10,000,000	10,000,000
Total interest and commitments fees	$ 2,000,000	$ 2,000,000