Loans - Allowance for Loan Losses (Detail) (USD $)
In Thousands, unless otherwise specified
 3 Months Ended 12 Months Ended
Dec. 31, 2013
Sep. 30, 2013
Jun. 30, 2013
Mar. 31, 2013
Dec. 31, 2012
Sep. 30, 2012
Jun. 30, 2012
Mar. 31, 2012
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Financing Receivable, Allowance for Credit Losses [Line Items]                      
Beginning balance       $ 20,504       $ 13,053 $ 20,504 $ 13,053 $ 10,155
Provision (credit) for loan losses 1,840 151 3,219 1,260 2,803 2,344 2,170 1,264 6,470 8,581 3,663
Charge-offs                 (2,560) (2,004) (1,502)
Recoveries                 921 874 737
Ending balance 25,335       20,504       25,335 20,504 13,053
Amount of allowance for loan losses for loans deemed to be impaired 376       649       376 649  
Amount of allowance for loan losses for loans not deemed to be impaired 24,959       19,855       24,959 19,855  
Total, Amount of allowance 25,335       20,504       25,335 20,504 13,053
Amount of allowance for loan losses for loans acquired with deteriorated credit quality included above 56       130       56 130  
Loans deemed to be impaired 33,472       41,181       33,472 41,181  
Loans not deemed to be impaired 2,258,784       1,765,756       2,258,784 1,765,756  
Total, Amount of allowance impaired 2,292,256       1,806,937       2,292,256 1,806,937  
One-to Four-Family [Member]
                      
Financing Receivable, Allowance for Credit Losses [Line Items]                      
Beginning balance       2,507       1,861 2,507 1,861 1,130
Provision (credit) for loan losses                 (217) 919 795
Charge-offs                 (531) (599) (192)
Recoveries                 232 326 128
Ending balance 1,991       2,507       1,991 2,507 1,861
Amount of allowance for loan losses for loans deemed to be impaired 132       128       132 128  
Amount of allowance for loan losses for loans not deemed to be impaired 1,859       2,379       1,859 2,379  
Total, Amount of allowance 1,991       2,507       1,991 2,507 1,861
Amount of allowance for loan losses for loans acquired with deteriorated credit quality included above 44       31       44 31  
Loans deemed to be impaired 4,089       4,486       4,089 4,486  
Loans not deemed to be impaired 450,059       438,742       450,059 438,742  
Total, Amount of allowance impaired 454,148       443,228       454,148 443,228  
Multi-Family Residential Real Estate [Member]
                      
Financing Receivable, Allowance for Credit Losses [Line Items]                      
Beginning balance       1,431       1,361 1,431 1,361 1,038
Provision (credit) for loan losses                 1,084 114 280
Charge-offs                 (96) (72)   
Recoveries                    28 43
Ending balance 2,419       1,431       2,419 1,431 1,361
Amount of allowance for loan losses for loans deemed to be impaired          90          90  
Amount of allowance for loan losses for loans not deemed to be impaired 2,419       1,341       2,419 1,341  
Total, Amount of allowance 2,419       1,431       2,419 1,431 1,361
Amount of allowance for loan losses for loans acquired with deteriorated credit quality included above          90          90  
Loans deemed to be impaired 4,002       5,784       4,002 5,784  
Loans not deemed to be impaired 284,170       173,164       284,170 173,164  
Total, Amount of allowance impaired 288,172       178,948       288,172 178,948  
Home Equity Lines of Credit [Member]
                      
Financing Receivable, Allowance for Credit Losses [Line Items]                      
Beginning balance       226       245 226 245 227
Provision (credit) for loan losses                 (71) 33 136
Charge-offs                    (52) (123)
Recoveries                       5
Ending balance 155       226       155 226 245
Amount of allowance for loan losses for loans deemed to be impaired                          
Amount of allowance for loan losses for loans not deemed to be impaired 155       226       155 226  
Total, Amount of allowance 155       226       155 226 245
Amount of allowance for loan losses for loans acquired with deteriorated credit quality included above                          
Loans deemed to be impaired 21       22       21 22  
Loans not deemed to be impaired 54,478       60,885       54,478 60,885  
Total, Amount of allowance impaired 54,499       60,907       54,499 60,907  
Commercial Real Estate [Member]
                      
Financing Receivable, Allowance for Credit Losses [Line Items]                      
Beginning balance       10,405       6,980 10,405 6,980 5,238
Provision (credit) for loan losses                 2,426 3,917 1,875
Charge-offs                    (719) (150)
Recoveries                    227 17
Ending balance 12,831       10,405       12,831 10,405 6,980
Amount of allowance for loan losses for loans deemed to be impaired 190       204       190 204  
Amount of allowance for loan losses for loans not deemed to be impaired 12,641       10,201       12,641 10,201  
Total, Amount of allowance 12,831       10,405       12,831 10,405 6,980
Amount of allowance for loan losses for loans acquired with deteriorated credit quality included above 12       9       12 9  
Loans deemed to be impaired 10,820       12,146       10,820 12,146  
Loans not deemed to be impaired 1,021,588       783,496       1,021,588 783,496  
Total, Amount of allowance impaired 1,032,408       795,642       1,032,408 795,642  
Construction [Member]
                      
Financing Receivable, Allowance for Credit Losses [Line Items]                      
Beginning balance       3,656       1,430 3,656 1,430 2,042
Provision (credit) for loan losses                 1,525 2,382 (240)
Charge-offs                 (1,362) (398) (869)
Recoveries                 555 242 497
Ending balance 4,374       3,656       4,374 3,656 1,430
Amount of allowance for loan losses for loans deemed to be impaired 54       227       54 227  
Amount of allowance for loan losses for loans not deemed to be impaired 4,320       3,429       4,320 3,429  
Total, Amount of allowance 4,374       3,656       4,374 3,656 1,430
Amount of allowance for loan losses for loans acquired with deteriorated credit quality included above                          
Loans deemed to be impaired 13,308       18,319       13,308 18,319  
Loans not deemed to be impaired 195,491       154,936       195,491 154,936  
Total, Amount of allowance impaired 208,799       173,255       208,799 173,255  
Commercial Business Loans [Member]
                      
Financing Receivable, Allowance for Credit Losses [Line Items]                      
Beginning balance       2,174       1,061 2,174 1,061 448
Provision (credit) for loan losses                 1,523 1,102 685
Charge-offs                 (288)    (72)
Recoveries                 24 11   
Ending balance 3,433       2,174       3,433 2,174 1,061
Amount of allowance for loan losses for loans deemed to be impaired                          
Amount of allowance for loan losses for loans not deemed to be impaired 3,433       2,174       3,433 2,174  
Total, Amount of allowance 3,433       2,174       3,433 2,174 1,061
Amount of allowance for loan losses for loans acquired with deteriorated credit quality included above                          
Loans deemed to be impaired 1,232       424       1,232 424  
Loans not deemed to be impaired 245,773       147,390       245,773 147,390  
Total, Amount of allowance impaired 247,005       147,814       247,005 147,814  
Consumer [Member]
                      
Financing Receivable, Allowance for Credit Losses [Line Items]                      
Beginning balance       105       115 105 115 32
Provision (credit) for loan losses                 200 114 132
Charge-offs                 (283) (164) (96)
Recoveries                 110 40 47
Ending balance 132       105       132 105 115
Amount of allowance for loan losses for loans deemed to be impaired                          
Amount of allowance for loan losses for loans not deemed to be impaired 132       105       132 105  
Total, Amount of allowance 132       105       132 105 115
Amount of allowance for loan losses for loans acquired with deteriorated credit quality included above                          
Loans deemed to be impaired                          
Loans not deemed to be impaired 7,225       7,143       7,225 7,143  
Total, Amount of allowance impaired 7,225       7,143       7,225 7,143  
Unallocated [Member]
                      
Financing Receivable, Allowance for Credit Losses [Line Items]                      
Beginning balance                           
Provision (credit) for loan losses                         
Charge-offs                         
Recoveries                         
Ending balance                           
Amount of allowance for loan losses for loans deemed to be impaired                          
Amount of allowance for loan losses for loans not deemed to be impaired                          
Total, Amount of allowance                           
Amount of allowance for loan losses for loans acquired with deteriorated credit quality included above                          
Loans deemed to be impaired                          
Loans not deemed to be impaired                          
Total, Amount of allowance impaired