Non Vested Base Restricted Stock Unit Activity Under Plans (Detail) - Restricted Stock With Performance and Market Based Vesting Conditions - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, Non-vested units as of December 31, 2014	860,000
Shares, Non-vested units as of December 31, 2015	860,000	860,000
Weighted Average Grant Date Fair Value, Non-vested units as of December 31, 2014	$ 34.66
Weighted Average Grant Date Fair Value, Non-vested units as of December 31, 2015	$ 34.66	$ 34.66
Weighted Average Remaining Years, Non-vested units as of December 31, 2014	2 months 12 days	1 year 2 months 12 days
Aggregate Intrinsic Value, Non-vested units as of December 31, 2014	$ 77,744
Aggregate Intrinsic Value, Non-vested units as of December 31, 2015	$ 90,094	$ 77,744