Investment Securities (Details 1) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Fair Value	$ 90,290	$ 316,746
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Gross Unrealized Losses	(327)	(2,032)
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Fair Value	1,103,263	1,706,835
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Gross Unrealized Losses	(12,479)	(38,258)
Unrealized Losses on Securities Available-for-Sale, Fair Value	1,193,553	2,023,581
Unrealized Losses on Securities Available-for-Sale, Gross Unrealized Losses	(12,806)	(40,290)
Government agency and government-sponsored enterprise pass through securities
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Fair Value	0	60,164
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Gross Unrealized Losses	0	(169)
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Fair Value	80,472	85,245
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Gross Unrealized Losses	(998)	(2,131)
Unrealized Losses on Securities Available-for-Sale, Fair Value	80,472	145,409
Unrealized Losses on Securities Available-for-Sale, Gross Unrealized Losses	(998)	(2,300)
Government agency and government-sponsored enterprise collateralized mortgage obligations
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Fair Value	0	69,859
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Gross Unrealized Losses	0	(326)
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Fair Value	148,729	164,097
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Gross Unrealized Losses	(2,939)	(5,046)
Unrealized Losses on Securities Available-for-Sale, Fair Value	148,729	233,956
Unrealized Losses on Securities Available-for-Sale, Gross Unrealized Losses	(2,939)	(5,372)
Private label collateralized mortgage obligations
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Fair Value	10,003	32,170
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Gross Unrealized Losses	(6)	(831)
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Fair Value	74,242	49,237
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Gross Unrealized Losses	(933)	(1,262)
Unrealized Losses on Securities Available-for-Sale, Fair Value	84,245	81,407
Unrealized Losses on Securities Available-for-Sale, Gross Unrealized Losses	(939)	(2,093)
Municipal securities
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Fair Value	0	52,386
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Gross Unrealized Losses	0	(238)
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Fair Value	119,130	284,915
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Gross Unrealized Losses	(1,710)	(7,082)
Unrealized Losses on Securities Available-for-Sale, Fair Value	119,130	337,301
Unrealized Losses on Securities Available-for-Sale, Gross Unrealized Losses	(1,710)	(7,320)
Government agency and government-sponsored enterprise commercial mortgage-backed securities
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Fair Value	0	40,641
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Gross Unrealized Losses	0	(341)
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Fair Value	611,315	1,020,684
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Gross Unrealized Losses	(5,365)	(21,184)
Unrealized Losses on Securities Available-for-Sale, Fair Value	611,315	1,061,325
Unrealized Losses on Securities Available-for-Sale, Gross Unrealized Losses	(5,365)	(21,525)
US Treasury Securities
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Fair Value		49,729
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Gross Unrealized Losses		(88)
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Fair Value		0
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Gross Unrealized Losses		0
Unrealized Losses on Securities Available-for-Sale, Fair Value		49,729
Unrealized Losses on Securities Available-for-Sale, Gross Unrealized Losses		(88)
Asset-backed Securities
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Fair Value	80,287	11,548
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Gross Unrealized Losses	(321)	(38)
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Fair Value	19,136	35,859
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Gross Unrealized Losses	(195)	(443)
Unrealized Losses on Securities Available-for-Sale, Fair Value	99,423	47,407
Unrealized Losses on Securities Available-for-Sale, Gross Unrealized Losses	(516)	(481)
SBA asset-backed securities
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Fair Value	0	249
Unrealized Losses on Securities Available-for-Sale, Less than 12 Months, Gross Unrealized Losses	0	(1)
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Fair Value	50,239	66,798
Unrealized Losses on Securities Available-for-Sale, 12 Months or Longer, Gross Unrealized Losses	(339)	(1,110)
Unrealized Losses on Securities Available-for-Sale, Fair Value	50,239	67,047
Unrealized Losses on Securities Available-for-Sale, Gross Unrealized Losses	$ (339)	$ (1,111)