Summary of Significant Accounting Policies - Supplemental Cash Flow Information (Details) - USD ($)		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Accounting Policies [Abstract]
Noncash or Part Noncash Acquisition, Noncash Financial or Equity Instrument Consideration, Shares Issued	[1]			0	1,858,133,000
Cash Transactions:
Interest paid				$ 136,154,000	$ 56,804,000
Income taxes paid, net				55,525,000	53,199,000
Noncash Transactions:
Loans charged-off to the allowance for loan losses		$ 6,949,000	$ 5,987,000	22,316,000	16,308,000
Loans foreclosed upon and transferred to other real estate owned				2,066,000	3,573,000
Loans foreclosed upon and transferred to other assets				1,580,000	641,000
Other Real Estate Sales Financed				276,000	0
Available-for-sale securities transferred to Held-to-Maturity				179,763,000	0
Transfer of Loans Held-for-sale to Portfolio Loans				$ 44,980,000	$ 0

[1] See Note 2 to these consolidated financial statement for more detailed information.