Basis of Presentation (Details 2) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended			9 Months Ended
	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Reconciliation of basic earnings per share ("EPS") to diluted EPS
Net income available to common stockholders	$ 20,006	$ 5,882	$ 12,976	$ 43,303	$ 36,036
Basic weighted-average shares outstanding	48,377		48,346	48,482	48,322
Dilutive effect of potential common stock equivalents - stock options (in shares)	174		44	121	63
Diluted weighted-average shares outstanding	48,551		48,390	48,603	48,385
Earnings per common share - basic:
Basic (in dollars per share)	$ 0.41		$ 0.27	$ 0.89	$ 0.75
Earnings per common share - diluted:
Diluted (in dollars per share)	$ 0.41		$ 0.27	$ 0.89	$ 0.74
Potentially dilutive securities excluded from earnings per diluted share because their effect is anti-dilutive (in shares)			1,709		1,714