Basis of Presentation (Details 4) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2013
Reconciliation of basic earnings per share ("EPS") to diluted EPS
Net income available to common stockholders	$ 20,451	$ 18,502	$ 32,538	$ 27,674	$ 23,297
Basic weighted-average shares outstanding	49,011	48,529	48,955		48,532
Dilutive effect of potential common stock equivalents — stock options and restricted stock units	216	99	191		95
Diluted weighted-average shares outstanding	49,227	48,628	49,146		48,627
Earnings per common share:
Basic (in dollars per share)	$ 0.42	$ 0.38	$ 0.66		$ 0.48
Diluted (in dollars per share)	$ 0.42	$ 0.38	$ 0.66		$ 0.48
Potentially dilutive securities excluded from earnings per diluted share because their effect is anti-dilutive	0	0	0		0