CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock [Member]	Common Stock and Paid in Capital [Member]	Retained Earnings (Accumulated Deficit) [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Unearned Restricted ESOP Shares [Member]
Balance, beginning of the period (in shares) at Dec. 31, 2013		19,543,769
Balance, beginning of the period at Dec. 31, 2013	$ 538,331		$ 569,028	$ (25,714)	$ (2,996)	$ (1,987)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	54,070			54,070
Other comprehensive income, net of income tax	2,738				2,738
Accrual of dividends on common stock	(14,092)			(14,092)
Redemption of unallocated shares upon termination of ESOP (in shares)		(34,340)
Redemption of unallocated shares upon termination of ESOP	0		(1,987)			1,987
Repurchase of shares upon termination of ESOP (in shares)		(13,550)
Repurchase of shares upon termination of ESOP	(555)		(555)
Proceeds from issuance of common stock for stockholder reinvestment program (in shares)		3,170
Proceeds from issuance of common stock for stockholder reinvestment program	127		127
Issuance of restricted stock and recognition of share-based compensation (in shares)		72,499
Issuance of restricted stock and recognition of share-based compensation	2,269		2,269
Balance, end of the period (in 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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	25,383			25,383
Other comprehensive income, net of income tax	485				485
Accrual of dividends on common stock	(7,551)			(7,551)
Proceeds from issuance of common stock for stockholder reinvestment program (in shares)		810
Proceeds from issuance of common stock for stockholder reinvestment program	33		33
Issuance of restricted stock and recognition of share-based compensation (in shares)		78,469
Issuance of restricted stock and recognition of share-based compensation	1,313		1,313
Issuance of shares for acquisitions (in shares)		1,319,854
Issuance of shares for acquisitions	58,099		58,099
Balance, end of the period (in shares) at Jun. 30, 2015		20,970,681
Balance, end of the period at Jun. 30, 2015	$ 660,650		$ 628,327	$ 32,096	$ 227	$ 0