Loan Sales and Servicing - Real Estate Mortgages Sold With Retained Servicing (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value of MSRs		$ 53,025		$ 49,597
Residential Real Estate Mortgage Loans Sold with Retained Servicing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Residential mortgage loans sold		132,470	$ 172,206
Servicing fees recognized	[1]	2,800	$ 2,805
Recorded balance of residential real estate mortgage loans sold with retained servicing	[2]	4,600,014		4,635,334
Fair value of MSRs	[3]	$ 53,025		$ 49,597

[1] Beginning in 2018, recorded as a component of mortgage banking in the Company's Unaudited Condensed Consolidated Statements of Income. 2017 servicing fees are recorded as a component of other noninterest income in the Company's Unaudited Condensed Consolidated Statements of Income.

[2] These loans are not included in loans on the Company's Unaudited Condensed Consolidated Balance Sheets.

[3] Recorded under the fair value method and included in other assets on the Company's Unaudited Condensed Consolidated Balance Sheets.