Segment Reporting (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Segment Reporting Information [Line Items]
Net interest income	$ 38,667	$ 38,193
Provision for loan and lease losses	637	2,354
Total noninterest income	26,468	23,388
Total noninterest expense	46,747	40,140
Income before taxes	17,751	19,087
Segment Assets	4,900,558	4,312,851	4,990,553
Average Loans	2,876,960	2,577,429
Community and Other Banking
Segment Reporting Information [Line Items]
Net interest income	38,333	37,787
Provision for loan and lease losses	637	2,354
Total noninterest income	13,400	13,900
Total noninterest expense	34,905	31,903
Income before taxes	16,191	17,430
Segment Assets	4,783,247	4,191,870
Average Loans	2,784,785	2,495,962
Retail Mortgage Banking
Segment Reporting Information [Line Items]
Net interest income	334	406
Provision for loan and lease losses	0	0
Total noninterest income	13,068	9,488
Total noninterest expense	11,842	8,237
Income before taxes	1,560	1,657
Segment Assets	117,311	120,981
Average Loans	$ 92,175	$ 81,467