Stockholders' Equity (Details) (USD $)	0 Months Ended	3 Months Ended	12 Months Ended
	Sep. 28, 2010	Dec. 31, 2010	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012
Sale of common stock in initial public offering (in shares)	19,435,000
Shares issued pursuant to the exercise of underwriters' over-allotment option	2,535,000
Price per share (in dollars per share)	$ 16.00
Gross proceeds from IPO	$ 311,000,000	$ 310,960,000
Proceeds net of underwriters' discounts, commissions and other offering costs from IPO	285,600,000
Underwriters' discounts, commissions and other offering costs	$ 25,300,000			$ 17,000	$ 25,306,000
Cash dividend (in dollars per share)			$ 0.27	$ 0.18		$ 0.18	$ 0.18	$ 0.18
Cumulative cash dividend for the year (in dollars per share)			$ 0.81
Ordinary Taxable Dividend (in dollars per share)			$ 0.27	$ 0.18		$ 0.18	$ 0.18	$ 0.18
Ordinary Taxable Dividend (in dollars per share)			$ 0.81
2010 Plan | Restricted stock
Granted (in shares)			405,608	263,393	185,437
2010 Plan | Options
Granted (in shares)			236,893	543,380	587,555
2010 Plan | Restricted stock units
Granted (in shares)			7,172	10,080	10,000