Earnings Per Share Earnings Per Share - Reconciliation (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Earnings Per Share [Abstract]
Numerator for basic and diluted EPS — net income allocated to common stockholders	$ 15,487	$ 2,242	$ 29,104	$ 18,376
Denominator for basic EPS — weighted average number of shares (shares)	29,912,161	30,507,700	30,131,291	30,649,957
Add — dilutive effect of:
Weighted average number of incremental shares issuable from restricted stock units (shares)	8,000	5,000	40,000	6,000
Denominator for diluted EPS — weighted average number of shares and dilutive potential shares (shares)	29,920,179	30,512,613	30,171,500	30,656,429
Earnings per share:
Basic (usd per share)	$ 0.52	$ 0.07	$ 0.97	$ 0.60
Diluted (usd per share)	$ 0.52	$ 0.07	$ 0.96	$ 0.60