Condensed Financial Statements of Parent Company - Condensed Statements of Cash Flows - (Details 3) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash flows from operating activities:
Net income	$ 99,473	$ 75,437	$ 49,219
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	21,470	21,180	17,495
Share-based Compensation.	5,803	3,908	3,322
Decrease (increase) in other assets	(4,861)	(4,687)	(3,320)
Decrease in Other Liabilities	(1,951)	(21,159)	4,522
Net cash provided by operating activities	186,868	118,647	242,405
Cash flows from investing activities:
Proceeds from calls of other investment securities	1,392
Net cash outlay for acquisitions	403,548		173,503
Net cash provided by investing activities	(103,015)	(9,497)	418,423
Cash flows from financing activities:
Common stock issuance	908	826	781
Common stock repurchase	(5,631)	(917)	(933)
Dividends paid on preferred stock		(1,073)	(1,354)
Dividends paid on common stock	(23,710)	(19,785)	(15,274)
Stock options exercised	1,115	709	1,885
Net cash provided by (used in) financing activities	194,072	(170,742)	(562,231)
Net increase in cash and cash equivalents	277,925	(61,592)	98,597
Cash and cash equivalents at beginning of period	417,869	479,461	380,864
Cash and cash equivalents at end of period	695,794	417,869	479,461
Parent company
Cash flows from operating activities:
Net income	99,473	75,437	49,219
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	355	339	264
Share-based Compensation.	5,803	3,908	3,322
Decrease (increase) in other assets	(296)	852	1,231
Decrease in Other Liabilities	(1,648)	(715)	(788)
Undistributed earnings of subsidiary	(22,578)	6,670	(35,795)
Net cash provided by operating activities	81,109	86,491	17,453
Cash flows from investing activities:
Proceeds from calls of other investment securities	1,392
Payments for investments in subsidiary	(384)
Net cash outlay for acquisitions			2,557
Proceeds from business divestitures			520
Other, net		177
Net cash provided by investing activities	1,008	177	3,077
Cash flows from financing activities:
Repayment of other borrowings	(46,392)
Common stock issuance	908	826	781
Common stock repurchase	(5,631)	(917)	(933)
Preferred stock redeemed		(65,000)
Dividends paid on preferred stock		(1,073)	(1,354)
Dividends paid on common stock	(23,710)	(19,785)	(15,274)
Stock options exercised	1,115	709	1,885
Net cash provided by (used in) financing activities	(73,710)	(85,240)	(14,895)
Net increase in cash and cash equivalents	8,407	1,428	5,635
Cash and cash equivalents at beginning of period	13,185	11,757	6,122
Cash and cash equivalents at end of period	$ 21,592	$ 13,185	$ 11,757