Parent Company Financial Information (Condensed Statements of Income) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Income
Interest-earning deposits									$ 179		$ 355		$ 854
Expense
Compensation and employee benefits									130,864		125,432		85,434
Other borrowings									593		734		479
Other expense									27,045	[1]	29,962	[1]	20,961	[1]
Income before income taxes	28,087	31,188	29,870	28,640	27,884	20,010	22,005	17,111	117,785		87,010		63,705
Income tax expense (benefit)	9,167	9,605	8,643	8,796	7,911	6,734	7,414	4,935	36,211		26,994		17,562
Net income (loss)	18,920	21,583	21,227	19,844	19,973	13,276	14,591	12,176	81,574		60,016		46,143
Parent Company [Member]
Income
Dividend from banking subsidiaries									16,200		183,000		48,950
Interest-earning deposits									25		68		153
Other income									10		7		0
Total Income									16,235		183,075		49,103
Expense
Compensation and employee benefits									530		658		182
Other borrowings									83		258		0
Other expense									1,433		4,162		1,193
Total Expenses									2,046		5,078		1,375
Income before income taxes									14,189		177,997		47,728
Income tax expense (benefit)									(704)		(1,552)		(435)
Income before equity in undistributed net income (loss) of subsidiaries									14,893		179,549		48,163
Equity in undistributed net income (loss) of subsidiaries									66,681		(119,533)		(2,020)
Net income (loss)									$ 81,574		$ 60,016		$ 46,143

[1] (1) Reclassified to conform to the current period’s presentation. The reclassification was limited to removing the separate line item for FDIC clawback liability expense within noninterest expense and including the prior period activity in the line item for other noninterest expense as well as removing the separate line item for provision for losses on covered loans and including the prior period activity in the line item for provision for loan and lease losses.