Mortgage Segment Reporting (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Segment Reporting Information [Line Items]
Net Interest Income	$ 37,974	$ 36,812	$ 37,177	$ 38,193	$ 36,837	$ 36,235	$ 36,601	$ 35,721	$ 150,156	$ 145,394	$ 143,052
Provision for loan losses	3,350	(502)	3,000	2,354	7,784	7,727	3,845	10,009	8,202	29,365	32,508
Total noninterest income	27,230	29,766	28,278	23,388	19,038	13,262	14,669	12,608	108,662	59,577	52,329
Total noninterest expense	54,623	47,159	41,459	40,140	40,203	31,863	32,343	32,887	183,381	137,296	129,239
Income before income taxes									67,235	38,310	33,634
Segment Assets	4,990,553				4,305,058				4,990,553	4,305,058
Average Loans									2,696,452	2,418,864
Community and Other Banking
Segment Reporting Information [Line Items]
Net Interest Income									147,903	145,098
Provision for loan losses									8,202	29,365
Total noninterest income									50,947	44,757
Total noninterest expense									144,146	123,660
Income before income taxes									46,502	36,830
Segment Assets	4,868,618				4,237,922				4,868,618	4,237,922
Average Loans									2,605,151	2,394,087
Mortgage banking operations
Segment Reporting Information [Line Items]
Net Interest Income									2,253	296
Provision for loan losses									0	0
Total noninterest income									57,715	14,820
Total noninterest expense									39,235	13,636
Income before income taxes									20,733	1,480
Segment Assets	121,935				67,136				121,935	67,136
Average Loans									$ 91,301	$ 24,777