Business Combinations (Unaudited Pro forma Information) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011
Disclosure - Unaudited Pro forma Information [Abstract]
Total Revenue	$ 514,278	[1]	$ 463,779	[1]
Net Income available to common shareholders	$ 114,690	[1]	$ 51,468	[1]
Earnings per share, diluted (dollars per share)	$ 2.56	[1]	$ 1.26	[1]

[1] Pro forma adjustments for certain acquisitions are excluded as they had no pre-acquisition operating activity in 2011 or 2012.