Stockholders' Equity - Award Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Dec. 31, 2015	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Stock option activity, Shares
Exercised (in shares)		0
Share-based compensation, additional disclosures
Total intrinsic value of options exercised	$ 5,363		$ 295
Total cash received from options exercised	$ 3,684		$ 729
Performance share award, TSR award, and restricted stock award activity, Shares
Nonvested at the beginning of the period (in shares)		0	0
Granted (in shares)		0	0
Canceled/forfeited (in shares)			0
Vested (in shares)			0
Nonvested at the end of the period (in shares)			0	0
Performance share award, TSR award, and restricted stock award activity, Weighted Average Exercise Price
Nonvested at beginning of the period, Weighted average grant date fair value (in dollars per share)	$ 77.02	$ 83.91	$ 65.42
Granted, Weighted average grant date fair value (in dollars per share)	74.88	81.88	114.65
Converted in Merger, Weighted Average Grant Date Fair Value		71.29
Canceled/forfeited, Weighted average grant date fair value (in dollars per share)	80.88	87.05	68.65
Vested, Weighted average grant date fair value (in dollars per share)	43.87	72.50	66.60
Nonvested at end of the period, Weighted average grant date fair value (in dollars per share)	$ 75.57	$ 77.02	$ 83.91	$ 65.42
Performance Share and TSR Awards
Performance share award, TSR award, and restricted stock award activity, Shares
Nonvested at the beginning of the period (in shares)	160,530	308,092	491,016
Granted (in shares)	2,976	161,661	113,212
Canceled/forfeited (in shares)	(5,374)	(309,223)	(200,557)
Vested (in shares)	(333)	0	(95,579)
Nonvested at the end of the period (in shares)	157,799	160,530	308,092	491,016
Restricted Stock Unit
Performance share award, TSR award, and restricted stock award activity, Shares
Nonvested at the beginning of the period (in shares)	500,939
Granted (in shares)	0
Converted in conjunction with the Merger		647,436
Canceled/forfeited (in shares)	(10,908)	0
Vested (in shares)	(191,084)	(146,497)
Nonvested at the end of the period (in shares)	298,947	500,939
Restricted Stock Award
Performance share award, TSR award, and restricted stock award activity, Shares
Nonvested at the beginning of the period (in shares)	212,635	282,944	267,426
Granted (in shares)	86,108	139,094	127,451
Canceled/forfeited (in shares)	(9,914)	(13,521)	(13,526)
Vested (in shares)	(17,806)	(195,882)	(98,407)
Nonvested at the end of the period (in shares)	271,023	212,635	282,944	267,426
Stock options
Stock option activity, Shares
Outstanding at beginning of period (in shares)	354,730	270,405	262,248
Granted (in shares)	1,443	73,100	47,490
Exercised (in shares)	(122,893)		(13,173)
Forfeited/expired (in shares)			(26,160)
Converted in conjunction with the Merger (in shares)		11,225
Outstanding at end of period (in shares)	233,280	354,730	270,405	262,248
Options exercisable at end of period (in shares)	109,509	230,715	114,083
Stock option activity, Weighted Average Exercise Price
Outstanding at beginning of period (in dollars per share)	$ 41.83	$ 74.11	$ 61.72
Granted (in dollars per share)	73.13	72.06	130.86
Exercised (in dollars per share)	30.90		55.32
Forfeited/expired (in dollars per share)			62.34
Converted in conjunction with the Merger (in dollars per share)		27.45
Outstanding at end of period (in dollars per share)	47.79	41.83	74.11	$ 61.72
Options exercisable at end of period (in dollars per share)	$ 32.43	$ 64.32	$ 61.63
Weighted Average Remaining Contractual Term
Options outstanding, Weighted Average Remaining Contractual Life (in years)	7 years 7 months 29 days	7 years 9 months 29 days	8 years 3 months 18 days	2 years 8 months 12 days
Options exercisable, Weighted Average Remaining Contractual Life (in years)	6 years 7 months 12 days	7 years	8 years
Aggregate Intrinsic Value
Options outstanding, Aggregate intrinsic value	$ 41.55	$ 34.80	$ 68.04
Options exercisable, Aggregate Intrinsic Value	$ 56.91	$ 44.99	$ 80.52
Performance share award, TSR award, and restricted stock award
Share-based compensation, additional disclosures
Total unrecognized compensation cost related to nonvested stock-based compensation awards	$ 29,320
Nonvested stock-based compensation expected to be realized over a weighted average period (in years)	2 years 2 months 12 days