Earnings Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Mar. 31, 2011
Numerator:
Net Income	$ 40,604	$ 45,483	$ 34,775	$ 56,645
Denominator:
Weighted average common stock shares outstanding - Basic	52,303	51,444	51,994	51,246
Assumed exercise of equity awards (in shares)	1,209	1,179	1,166	1,217
Weighted average common stock shares outstanding - Diluted	53,512	52,623	53,160	52,463
Net income per common share:
Basic (in dollars per share)	$ 0.78	$ 0.88	$ 0.67	$ 1.11
Diluted (in dollars per share)	$ 0.76	$ 0.86	$ 0.65	$ 1.08
Stock options
Anti-dilutive securities excluded from computation of diluted earnings per share
Antidilutive securities excluded from computation of earnings per share		83	522	90
Deferred stock
Anti-dilutive securities excluded from computation of diluted earnings per share
Antidilutive securities excluded from computation of earnings per share			58
Restricted stock
Anti-dilutive securities excluded from computation of diluted earnings per share
Antidilutive securities excluded from computation of earnings per share	1,031	607	1,494	664
Convertible notes
Anti-dilutive securities excluded from computation of diluted earnings per share
Antidilutive securities excluded from computation of earnings per share	10,943	10,943	10,943	10,943
Conversion price (in dollars per share)					$ 7.88
Warrants
Anti-dilutive securities excluded from computation of diluted earnings per share
Antidilutive securities excluded from computation of earnings per share	10,943	10,943	10,943	10,943
Exercise price (in dollars per share)					$ 10.00