Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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Stock-Based Compensation Plans (Narrative) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	May 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares approved for issuance (in shares)					5,485,000
Shares available for future grants (in shares)	2,100,000		2,100,000
Number of stock options granted			0	0
Stock-based compensation expense	$ 540	$ 3,000	$ (2,300)	$ 6,300
Aggregate intrinsic value of options exercised			2,700	3,300
Cash received from option exercises			$ 3,800	$ 3,600
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Term			7 years
Stock options \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			3 years
Stock options \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			5 years
Restricted shares \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			1 year
Restricted shares \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			5 years
LTIP awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			3 years
Term			7 years
LTIP awards \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of performance based award payouts			0.00%
LTIP awards \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of performance based award payouts			150.00%
Performance-based stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			3 years