CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock [Member]	Common Stock Including Additional Paid in Capital [Member]	Retained Earnings (Accumulated Deficit) [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Deferred Compensation, Share-based Payments [Member]
Balance, beginning of the period at Dec. 31, 2013	$ 538,331		$ 569,028	$ (25,714)	$ (2,996)	$ (1,987)
Balance, beginning of the period, shares at Dec. 31, 2013		19,543,769
Net income	54,070			54,070
Other comprehensive income (loss)	2,738				2,738
Accrual of dividends on common stock	(14,092)			(14,092)
Cash paid for repurchase of common stock	0
Redemption of unallocated shares upon termination of ESOP	0		(1,987)			1,987
Redemption of unallocated shares upon termination of ESOP, shares		(34,340)
Repurchase of shares upon termination of ESOP	(555)		(555)
Repurchase of shares upon termination of ESOP, shares		(13,550)
Proceeds from issuance of common stock for stockholder reinvestment program, net of registration expenses amount	127		127
Proceeds from issuance of common stock for stockholder reinvestment program shares		3,170
Amortization of share-based compensation related to restricted stock grants, net of shares surrendered	2,203		2,203
Issuance of unvested restricted common stock, net, shares		72,499
Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation	66
Balance, end of the period, shares at Dec. 31, 2014		19,571,548
Balance, end of the period at Dec. 31, 2014	582,888		568,882	14,264	(258)	0
Net income	45,222			45,222
Other comprehensive income (loss)	(472)				(472)
Accrual of dividends on common stock	(19,871)			(19,871)
Cash paid for repurchase of common stock	0
Proceeds from issuance of common stock for stockholder reinvestment program, net of registration expenses amount	34		34
Proceeds from issuance of common stock for stockholder reinvestment program shares		810
Amortization of share-based compensation related to restricted stock grants, net of shares surrendered	3,088		3,088
Issuance of unvested restricted common stock, net, shares		120,043
Stock Issued During Period, Value, Acquisitions	688,773
Stock Issued During Period, Shares, Acquisitions		14,549,854
Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation	397
Balance, end of the period, shares at Dec. 31, 2015		34,242,255
Balance, end of the period at Dec. 31, 2015	1,300,059		1,261,174	39,615	(730)	0
Net income	85,385			85,385
Other comprehensive income (loss)	(2,725)				(2,725)
Accrual of dividends on common stock	(29,672)			(29,672)
Cash paid for repurchase of common stock	(50,772)		50,772
Repurchase of shares upon termination of ESOP, shares		(1,145,250)
Amortization of share-based compensation related to restricted stock grants, net of shares surrendered	3,401		3,401
Issuance of unvested restricted common stock, net, shares		96,382
Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation	34
Balance, end of the period, shares at Dec. 31, 2016		33,193,387
Balance, end of the period at Dec. 31, 2016	$ 1,305,710		$ 1,213,837	$ 95,328	$ (3,455)	$ 0