Stock Compensation Plans and Other Employee Benefit Plans (Narrative) (Details)	12 Months Ended
	Dec. 31, 2018 USD ($) hour Rate shares	Dec. 31, 2017 USD ($) shares	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 shares	May 31, 2015 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for grant (in shares) | shares	3,400,000
Options granted (in shares) | shares	0	0	562,166
Stock-based compensation expense	$ 13,500,000	$ 12,900,000	$ 9,300,000
Tax benefit from stock-based compensation arrangements	3,100,000	5,100,000	$ 3,700,000
Options granted, weighted average grant date fair value (in dollars per share) | $ / shares			$ 8.61
Aggregate intrinsic value of options exercised	13,300,000	20,100,000	$ 5,800,000
Tax benefit realized from option exercises	3,500,000	7,800,000	2,300,000
Cash received from option exercises	11,700,000	24,100,000	11,800,000
Unrecognized compensation	$ 15,400,000
Unrecognized compensation period for recognition	2 years
Fair value of shares vested	$ 8,000,000	8,900,000	8,400,000
Number of hours of service required for eligibility | hour	501
Expense for employer contribution to plan	$ 10,400,000	8,900,000	6,600,000
Pension expense (income)	(38,000)	1,200,000	526,000
HPK Financial Corporation
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Projected benefit obligation	4,900,000
Fair value of plan assets	4,700,000
Diamond Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Projected benefit obligation	2,700,000
Fair value of plan assets	1,600,000
Cash Incentive And Retention Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expense related to plan	0	0	0
Cash awards paid	0	$ 0	$ 0
Cash awards outstanding	$ 0
Directors Deferred Fee And Stock Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Issued to directors (in shares) | shares	18,856	27,508	25,362
Obligation to issue (in shares) | shares	281,910
Available for future issuance (in shares) | shares	74,206
2015 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized (in shares) | shares					5,485,000
2015 and 2007 Plans | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares vested in period (in shares)	3 years
2015 and 2007 Plans | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares vested in period (in shares)	5 years
Option term	7 years
Restricted shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum number of shares that could be issued based on the grants made to date (in shares) | shares	143,263	127,787	133,425	137,593
Restricted shares | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares vested in period (in shares)	1 year
Restricted shares | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares vested in period (in shares)	5 years
LTIP awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares vested in period (in shares)	3 years
LTIP awards | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award payout percentage | Rate	0.00%
LTIP awards | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option term	7 years
Award payout percentage | Rate	150.00%
Performance shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum number of shares that could be issued based on the grants made to date (in shares) | shares	396,855	359,196	298,180	276,533
Excess tax benefit over estimate	$ 994,000	$ 975,000	$ 241,000
Performance shares | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum number of shares that could be issued based on the grants made to date (in shares) | shares	585,518
ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Purchase price of shares, percentage of closing price	95.00%
Employee stock purchase plan issuance (in shares) | shares	33,977	35,022	50,920
Compensation expense employee stock purchase plan	$ 0	$ 0	$ 0
Increase in shares authorized (in shares) | shares	200,000
Common stock obligation to issue (in shares) | shares	10,807
Available for future grants (in shares) | shares	216,063