Derivatives and Hedging Fair Value of Derivative Contracts (Detail) - USD ($) $ in Thousands		Mar. 31, 2016	Dec. 31, 2015	Dec. 31, 2013
Derivatives, Fair Value [Line Items]
Notional Amount		$ 797,304	$ 800,478	$ 670,942
Derivative Asset, Fair Value		4,733	3,569	7
Derivative Liability, Fair Value		88,981	64,785	73,049
Notional Amount, Netting Adjustments	[1]	0	0	0
Derivative Netting Adjustments	[1]	0	0	0
Positive NPVs		4,733	3,569	7
Negative NPVs		88,981	64,785	73,049
Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Notional Amount		797,304	800,478	670,942
Derivative Asset, Fair Value		4,733	3,569	7
Derivative Liability, Fair Value		$ 88,981	$ 64,785	$ 73,049

[1] Netting adjustments represent the amounts recorded to convert derivative balances from a gross basis to a net basis in accordance with the applicable accounting guidance.