Condensed Financial Information (Parent Company Only) - Condensed Statements of Income (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Condensed Financial Statements, Captions
Salaries and benefits	$ 94,002	$ 89,833	$ 83,560
Interest expense	20,695	30,114	42,031
Earnings before income tax benefit	132,702	88,262	66,161
Income tax benefit	46,566	30,038	21,615
Net income	86,136	58,224	44,546
Parent Company
Condensed Financial Statements, Captions
Dividends from subsidiaries	71,400	40,000	30,000
Other interest income	34	92	118
Other income, primarily management fees from subsidiaries	12,809	10,042	10,617
Total income	84,243	50,134	40,735
Salaries and benefits	15,914	13,205	13,975
Interest expense	4,098	6,691	7,273
Other operating expenses, net	7,546	7,150	6,903
Total expenses	27,558	27,046	28,151
Earnings before income tax benefit	56,685	23,088	12,584
Income tax benefit	(5,703)	(6,222)	(6,518)
Income before undistributed earnings of subsidiaries	62,388	29,310	19,102
Undistributed earnings of subsidiaries	23,748	28,914	25,444
Net income	$ 86,136	$ 58,224	$ 44,546