Consolidated Statement of Stockholders' Equity (Unaudited) (USD $) In Thousands, unless otherwise specified	Total	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]
Balance at Dec. 31, 2012	$ 1,402,069		$ 1,398	$ 1,376,601	$ 75,312	$ (46,224)	$ (5,018)
Net income	57,731				57,731
Change in other comprehensive income (loss), net of tax	(15,853)					(15,853)
Dividends declared:
Preferred stock
Common stock: $0.24/share	(34,468)				(34,468)
Issuance of common stock	56,178		56	58,066			(1,944)
Restricted stock compensation	2,094			2,094
Tax benefit of stock-based compensation	1,247			1,247
Balance at Jun. 30, 2013	1,468,998		1,454	1,438,008	98,575	(62,077)	(6,962)
Balance at Dec. 31, 2013	1,774,383	106,882	1,592	1,608,117	121,870	(56,924)	(7,154)
Net income	69,355				69,355
Change in other comprehensive income (loss), net of tax	20,365					20,365
Dividends declared:
Preferred stock	(4,332)				(4,332)
Common stock: $0.24/share	(40,123)				(40,123)
Issuance of common stock	4,116		14	7,857	(228)		(3,527)
Issuance of common stock-acquisitions	81,389		67	81,322
Restricted stock compensation	1,419			1,419
Tax benefit of stock-based compensation	1,505			1,505
Balance at Jun. 30, 2014	$ 1,908,077	$ 106,882	$ 1,673	$ 1,700,220	$ 146,542	$ (36,559)	$ (10,681)