Regulatory Capital (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2015
Parent Company
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Capital conservation buffer, ratio	2.50%		0.625%
Capital, amount	$ 1,094,062	$ 631,952
Capital to risk weighted assets, ratio	23.45%	15.01%
Capital required for capital adequacy, amount	$ 373,276	$ 336,730
Capital required for capital adequacy to risk weighted assets, ratio	8.00%	8.00%
Capital required for capital adequacy with capital buffer, amount	$ 460,763	$ 389,244
Capital required for capital adequacy with capital buffer to risk weighted assets, ratio	9.88%	9.25%
Tier one risk based capital, amount	$ 1,035,477	$ 579,080
Tier one risk based capital to risk weighted assets, ratio	22.19%	13.76%
Tier one risk based capital required for capital adequacy, amount	$ 279,957	$ 252,547
Tier one risk based capital required for capital adequacy to risk weighted assets, ratio	6.00%	6.00%
Tier one risk based capital required for capital adequacy with capital buffer, amount	$ 367,444	$ 305,161
Tier one risk based capital required for capital adequacy with capital buffer to risk weighted assets, ratio	7.88%	7.25%
Common equity tier one capital, amount	$ 1,035,477	$ 528,080
Common equity tier one capital ratio	22.19%	12.55%
Common equity tier one capital required for capital adequacy, amount	$ 209,968	$ 189,410
Common equity tier one capital required for capital adequacy to risk weighted assets, ratio	4.50%	4.50%
Common equity tier one risk based capital required for capital adequacy with capital buffer, amount	$ 297,455	$ 242,025
Common equity tier one risk based capital requirement for capital adequacy with capital buffer to risk weighted assets, ratio	6.38%	5.75%
Tier one leverage capital, amount	$ 1,035,477	$ 579,080
Tier one leverage capital to average assets, ratio	15.75%	10.54%
Tier one leverage capital required for capital adequacy, amount	$ 263,037	$ 219,833
Tier one leverage capital required for capital adequacy to average assets, ratio	4.00%	4.00%
Tier one leverage capital required for capital adequacy with capital buffer to average assets, amount	$ 263,037	$ 219,833
Tier one leverage capital requirement for capital adequacy with capital buffer to average assets, ratio	4.00%	4.00%
Subsidiaries
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Capital, amount	$ 886,728	$ 625,336
Capital to risk weighted assets, ratio	19.04%	14.90%
Capital required for capital adequacy, amount	$ 372,550	$ 335,736
Capital required for capital adequacy to risk weighted assets, ratio	8.00%	8.00%
Capital required for capital adequacy with capital buffer, amount	$ 459,866	$ 388,196
Capital required for capital adequacy with capital buffer to risk weighted assets, ratio	9.88%	9.25%
Capital required to be well capitalized, amount	$ 465,687	$ 419,671
Capital required to be well capitalized to risk weighted assets, ratio	10.00%	10.00%
Tier one risk based capital, amount	$ 828,257	$ 572,617
Tier one risk based capital to risk weighted assets, ratio	17.79%	13.64%
Tier one risk based capital required for capital adequacy, amount	$ 279,412	$ 251,802
Tier one risk based capital required for capital adequacy to risk weighted assets, ratio	6.00%	6.00%
Tier one risk based capital required for capital adequacy with capital buffer, amount	$ 366,729	$ 304,262
Tier one risk based capital required for capital adequacy with capital buffer to risk weighted assets, ratio	7.88%	7.25%
Tier one risk based capital required to be well capitalized, amount	$ 372,550	$ 335,736
Tier one risk based capital required to be well capitalized to risk weighted assets, ratio	8.00%	8.00%
Common equity tier one capital, amount	$ 828,257	$ 572,617
Common equity tier one capital ratio	17.79%	13.64%
Common equity tier one capital required for capital adequacy, amount	$ 209,559	$ 188,852
Common equity tier one capital required for capital adequacy to risk weighted assets, ratio	4.50%	4.50%
Common equity tier one risk based capital required for capital adequacy with capital buffer, amount	$ 296,875	$ 241,311
Common equity tier one risk based capital requirement for capital adequacy with capital buffer to risk weighted assets, ratio	6.38%	5.75%
Common equity tier one capital required to be well-capitalized, amount	$ 302,697	$ 272,786
Common equity tier one capital required to be well-capitalized to risk weighted assets, ratio	6.50%	6.50%
Tier one leverage capital, amount	$ 828,257	$ 572,617
Tier one leverage capital to average assets, ratio	12.60%	10.44%
Tier one leverage capital required for capital adequacy, amount	$ 263,025	$ 221,257
Tier one leverage capital required for capital adequacy to average assets, ratio	4.00%	4.00%
Tier one leverage capital required for capital adequacy with capital buffer to average assets, amount	$ 263,025	$ 221,257
Tier one leverage capital requirement for capital adequacy with capital buffer to average assets, ratio	4.00%	4.00%
Tier one leverage capital required to be well capitalized, amount	$ 328,781	$ 276,571
Tier one leverage capital required to be well capitalized to average assets, ratio	5.00%	5.00%