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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Net number of non-option equity instruments granted to participants.

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Equity-Based Compensation - The Amended Director Plan Additional Information (Detail) - $ / shares	3 Months Ended		12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares, vested	657,317	644,247
Number of shares, granted (in shares)	434,283	441,256
Weighted average fair value, granted (in dollars per share)	$ 8.44	$ 16.21
Deferred stock units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted	22,500
Deferred stock units \| Tranche Two
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock awards vesting period (in years)	2 years
Number of shares, vested	15,000
Non-Management Director Compensation Plan \| Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock awards vesting period (in years)	6 months
Prior Director Plan \| Deferred stock units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted	7,500
Prior Director Plan \| Deferred stock units \| Tranche One
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock awards vesting period (in years)	1 year
Number of shares, vested	7,500
Non Management Directors Director Plan, Retainer Fee, First Half of 2015 \| Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares, granted (in shares)		18,200
Weighted average fair value, granted (in dollars per share)		$ 16.10
Non Management Directors Director Plan, Retainer Fee, June 12, 2015 through June 12, 2016 \| Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares, granted (in shares)			50,416
Weighted average fair value, granted (in dollars per share)			$ 13.17
Non Management Directors Director Plan, Triennial Service Awards \| Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares, granted (in shares)			90,000
Non Management Directors Director Plan, Triennial Service Awards \| Restricted Stock \| Tranche One
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares, granted (in shares)			30,000
Non Management Directors Director Plan, Triennial Service Awards \| Restricted Stock \| Tranche Two
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares, granted (in shares)			60,000
Non Management Directors Director Plan, Triennial Service Awards \| Deferred stock units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares, granted (in shares)			90,000
Weighted average fair value, granted (in dollars per share)			$ 13.17
Non Management Directors Director Plan, Triennial Service Awards \| Deferred stock units \| Tranche One
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares, granted (in shares)			30,000
Non Management Directors Director Plan, Triennial Service Awards \| Deferred stock units \| Tranche Two
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares, granted (in shares)			60,000