CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Parent	Preferred Stock	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income	Retained Earnings (Accumulated Deficit).	Deferred Compensation Employee Stock Trust, Net	Employee Stock Trust	Noncontrolling Interest	Total
Balance at Dec. 31, 2014	$ 1,460,452	$ 114,068	$ 902	$ 1,390,788	$ 651	$ (45,957)			$ 787	$ 1,461,239
Balance (in shares) at Dec. 31, 2014		114	90,182
Increase (Decrease) in Stockholders' Equity
Net income	113,302					113,302			353	113,655
Other comprehensive income	5,099				5,099					5,099
Issuance of common stock	200,033		$ 101	199,932						200,033
Issuance of common stock (in shares)			10,113
Stock-based compensation expense	1,814			1,814						1,814
Common stock issued to board members	51			51						51
Common stock issued to board members (in shares)			2
Issuance of common stock related to share-based awards, net (in shares)			(11)
Dividends on preferred stock	(1,427)					(1,427)				(1,427)
Deferred compensation plan	592						$ 1,189	$ (597)		592
Deferred compensation plan (in shares)								30
Net cash distributed to noncontrolling interest									(264)	(264)
Balance at Mar. 31, 2015	1,779,916	$ 114,068	$ 1,003	1,592,585	5,750	65,918	1,189	$ (597)	876	1,780,792
Balance (in shares) at Mar. 31, 2015		114	100,286					30
Balance at Dec. 31, 2015	1,736,954		$ 989	1,577,270	2,629	155,475	1,034	$ (443)	1,171	1,738,125
Balance (in shares) at Dec. 31, 2015			98,896					22
Increase (Decrease) in Stockholders' Equity
Net income	27,567					27,567			629	28,196
Other comprehensive income	4,249				4,249					4,249
Issuance of common stock	3,850		$ 5	3,845						3,850
Issuance of common stock (in shares)			500
Stock-based compensation expense	2,228			2,228						2,228
Common stock issued to board members	108			108						108
Common stock issued to board members (in shares)			6
Issuance of common stock related to share-based awards, net	(33)			(33)						(33)
Issuance of common stock related to share-based awards, net (in shares)			(1)
Retirement of common stock	(16,276)		$ (8)	(16,268)						(16,276)
Retirement of common stock (in shares)			(816)
Deferred compensation plan	1						(14)	$ 15		1
Deferred compensation plan (in shares)								(1)
Net cash distributed to noncontrolling interest									(437)	(437)
Balance at Mar. 31, 2016	$ 1,758,648		$ 986	$ 1,567,150	$ 6,878	$ 183,042	$ 1,020	$ (428)	$ 1,363	$ 1,760,011
Balance (in shares) at Mar. 31, 2016			98,585					21