Investment Securities - (Summary of Unrealized Losses) (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	$ 296,379	$ 241,532
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(3,575)	(3,513)
12 months or more, Fair Value	365,901	385,707
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(12,259)	(13,025)
Total, Fair Value	662,280	627,239
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(15,834)	(16,538)
Residential Mortgage Pass-Through Securities Issued or Guaranteed by U.S. Government Agencies or Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	92,828	100,898
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(543)	(530)
Total, Fair Value	92,828	100,898
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(543)	(530)
Other Residential MBS Issued or Guaranteed by U.S. Government Agencies or Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	200,493	137,576
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(3,023)	(2,976)
12 months or more, Fair Value	365,901	385,707
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(12,259)	(13,025)
Total, Fair Value	566,394	523,283
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(15,282)	(16,001)
Municipal [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	3,058	3,058
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(9)	(7)
Total, Fair Value	3,058	3,058
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ (9)	$ (7)